added readme for nuget, updated reference from csproj

Author: petesramek

src/PolylineAlgorithm/PolylineAlgorithm.csproj

@@ -32,7 +32,7 @@
 	</PropertyGroup>
 
 	<ItemGroup>
-		<None Include="..\..\README.md">
+		<None Include=".\README.md">
 			<Pack>True</Pack>
 			<PackagePath>\</PackagePath>
 		</None>

src/PolylineAlgorithm/README.md

@@ -0,0 +1,79 @@
+# PolylineAlgorithm for .NET
+
+A modern, fully compliant Google Encoded Polyline Algorithm library for .NET Standard 2.1+, supporting strong input validation, extensibility for custom coordinate types, and robust performance.
+
+## Features
+
+- Google-compliant polyline encoding/decoding for geographic coordinates
+- Immutable, strongly-typed data structures: `Coordinate`, `Polyline`
+- Predefined encoder/decoder types for easy usage
+- Extensible APIs for custom coordinate and polyline types
+- Robust input validation and descriptive exceptions
+- Configurable with `PolylineEncodingOptions` (buffer, logging, etc.)
+- Thread-safe, stateless APIs
+- Benchmarks and unit tests for correctness and performance
+- Auto-generated API docs ([API Reference](https://petesramek.github.io/polyline-algorithm-csharp/))
+- Supports .NET Core, .NET 5+, Xamarin, Unity, Blazor via `netstandard2.1`
+
+## Installation
+
+```shell
+dotnet add package PolylineAlgorithm
+```
+
+or via NuGet PMC:
+
+```powershell
+Install-Package PolylineAlgorithm
+```
+
+## Quick Start
+
+### Encode coordinates
+
+```csharp
+using PolylineAlgorithm;
+
+var coordinates = new List<Coordinate>
+{
+    new Coordinate(48.858370, 2.294481),
+    new Coordinate(51.500729, -0.124625)
+};
+
+var encoder = new PolylineEncoder();
+Polyline encoded = encoder.Encode(coordinates);
+
+Console.WriteLine(encoded.ToString()); // Print encoded polyline string
+```
+
+### Decode polyline
+
+```csharp
+using PolylineAlgorithm;
+
+var decoder = new PolylineDecoder();
+Polyline polyline = Polyline.FromString("yseiHoc_MwacOjnwM");
+IEnumerable<Coordinate> decoded = decoder.Decode(polyline);
+```
+
+## Advanced Usage
+
+- Custom coordinate/polyline types are supported via `AbstractPolylineEncoder` and `AbstractPolylineDecoder`.
+- Additional configuration via `PolylineEncodingOptionsBuilder`.
+
+> See [API Reference](https://petesramek.github.io/polyline-algorithm-csharp/) for full documentation.
+
+## FAQ
+
+- **What coordinate ranges are valid?**  
+  Latitude: -90..90, Longitude: -180..180 (throws `ArgumentOutOfRangeException` for invalid input)
+- **What .NET versions are supported?**  
+  Any environment supporting `netstandard2.1`
+- **How do I customize encoder options?**  
+  Use `PolylineEncodingOptionsBuilder` and pass to the encoder constructor.
+- **Where can I get help?**  
+  [GitHub issues](https://github.com/petesramek/polyline-algorithm-csharp/issues)
+
+## License
+
+MIT License © Pete Sramek