Fix version switcher URL bug and improve docs navigation/landing page (#182)

Version switcher on the global index page produced broken URLs like
`.../index.html/1.0/PolylineAlgorithm.html`, and even when corrected
would land users on the raw API reference — a poor first-visit
experience. Introduction was also redundant as a separate guide entry.

## Changes

### `version-switcher.js`
- **URL fix**: `getSiteRoot()` treated an empty `docfx:rel` meta
attribute as a valid relative URL, causing `new URL('',
'.../index.html')` to resolve to the full page path including the
filename. Now falls back to `'./'` when the attribute is empty.
- **Better redirect from index**: Selecting a version on the global
index now navigates to `{version}/guide/getting-started.html` instead of
`{version}/PolylineAlgorithm.html`.

```js
// Before
return meta ? meta.getAttribute('content') : './';
// After — empty string is falsy, so we fall back to './'
return meta ? (meta.getAttribute('content') || './') : './';
```

### `api-reference/guide/toc.yml`
- Removed the **Introduction** entry; **Getting Started** is now the
first and default page in the versioned guide sidebar.

### `api-reference/index.md`
- Replaced the bare link list with a proper landing page: library
summary, key benefits, and a quick-start install snippet — content drawn
from `introduction.md`. The `{versions_section}` placeholder is
preserved for workflow injection.

### `publish-documentation.yml`
- Navbar `toc.yml` generation and the versions table both updated to
link to `getting-started.html` instead of the now-removed
`introduction.html`.

Author: petesramek

.github/workflows/publish-documentation.yml

@@ -139,7 +139,7 @@ jobs:
           {
             echo "### YamlMime:TableOfContent"
             echo "- name: Guide"
-            echo "  href: ${latest}/guide/introduction.html"
+            echo "  href: ${latest}/guide/getting-started.html"
             echo "- name: API Reference"
             echo "  href: ${latest}/PolylineAlgorithm.html"
           } > api-reference/toc.yml
@@ -159,7 +159,7 @@ jobs:
               else
                 label="v${ver}"
               fi
-              echo "| ${label} | [Guide](${ver}/guide/introduction.html) | [API Reference](${ver}/PolylineAlgorithm.html) |"
+              echo "| ${label} | [Guide](${ver}/guide/getting-started.html) | [API Reference](${ver}/PolylineAlgorithm.html) |"
             done
           } > /tmp/versions_section.md
           awk '/{versions_section}/{while((getline line < "/tmp/versions_section.md") > 0) print line; close("/tmp/versions_section.md"); next} {print}' \

api-reference/docs-versioning/public/version-switcher.js

@@ -13,7 +13,7 @@
 
   function getSiteRoot() {
     var meta = document.querySelector('meta[name="docfx:rel"]');
-    return meta ? meta.getAttribute('content') : './';
+    return meta ? (meta.getAttribute('content') || './') : './';
   }
 
   var VERSION_PATTERN = /\/\d+(\.\d+)*\//;
@@ -83,7 +83,7 @@
         );
       } else {
         var siteRootPath = new URL(getSiteRoot(), window.location.href).pathname.replace(/\/$/, '');
-        newPathname = siteRootPath + '/' + targetVersion + '/PolylineAlgorithm.html';
+        newPathname = siteRootPath + '/' + targetVersion + '/guide/getting-started.html';
       }
 
       window.location.pathname = newPathname;

api-reference/guide/toc.yml

@@ -1,6 +1,4 @@
-- name: Introduction
-  href: introduction.md
-- name: Getting Started
+- name: Getting Started
   href: getting-started.md
 - name: Configuration
   href: configuration.md

api-reference/index.md

@@ -1,20 +1,33 @@
-# PolylineAlgorithm API Reference
+# PolylineAlgorithm for .NET
 
-Welcome! This documentation provides guides, configuration options, examples, and FAQs for the PolylineAlgorithm library.  
-For detailed class and method docs, see the versioned [API Reference]({version}/PolylineAlgorithm.html).
+Welcome to **PolylineAlgorithm for .NET**, a modern library for Google-compliant polyline encoding and decoding with strong input validation, extensible API design, and robust performance.
 
-## Contents
+## What is PolylineAlgorithm?
 
-- [Introduction]({version}/guide/introduction.html)
-- [Getting Started]({version}/guide/getting-started.html)
-- [Configuration Options]({version}/guide/configuration.html)
-- [Advanced Scenarios]({version}/guide/advanced-scenarios.html)
-- [Samples]({version}/guide/sample.html)
-- [FAQ]({version}/guide/faq.html)
+PolylineAlgorithm provides tools for encoding a sequence of geographic coordinates into a compact string format used by Google Maps and other mapping platforms, and for decoding those strings back into coordinates. Its simple API and thorough documentation make it suitable for .NET Core, .NET 5+, and any framework supporting `netstandard2.1`.
+
+## Key Benefits
+
+- **Standards compliance**: Implements Google's Encoded Polyline Algorithm as specified
+- **Immutable, strongly-typed objects**: Guarantees reliability and thread safety
+- **Extensible**: Custom coordinate/polyline support via abstract base classes and interfaces
+- **Robust input validation**: Throws descriptive exceptions for out-of-range or malformed input
+- **Configuration and logging**: Advanced options and integration with `ILoggerFactory`
+- **Benchmarked and tested**: Includes unit and performance tests
+
+## Getting Started
+
+Install via the .NET CLI:
+
+```shell
+dotnet add package PolylineAlgorithm
+```
+
+Then explore the versioned guide and API reference below to learn more.
 
 {versions_section}
 
 ## Links
 
-- [API Reference]({version}/PolylineAlgorithm.html)
 - [Contributing Guidelines](https://github.com/petesramek/polyline-algorithm-csharp/blob/main/CONTRIBUTING.md)
+- [Report an Issue](https://github.com/petesramek/polyline-algorithm-csharp/issues)