seo: Add sitemap.xml, robots.txt, and fix canonical URL for Google indexing

- sitemap.xml pointing to GitHub Pages URL
- robots.txt allowing all crawlers with sitemap reference
- canonical URL corrected to https://ls-instruments.github.io/RepoHerd/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: AndreaV-Lsi

index.html

@@ -6,7 +6,8 @@
     <title>RepoHerd — Multi-Repository Git Dependency Manager</title>
     <meta name="description" content="Clone and checkout multiple Git repositories to pinned versions with automated dependency resolution. A cross-platform PowerShell tool for multi-repo version pinning, reproducible builds, and recursive dependency management. Alternative to git submodules for managing shared libraries.">
     <meta name="keywords" content="git clone multiple repositories, git dependency manager, version pinning, reproducible builds, powershell git automation, multi-repo, dependency resolution, semver, recursive dependencies, cross-platform, ssh, git submodule alternative, monorepo alternative, devops, version control">
-    <link rel="canonical" href="https://github.com/LS-Instruments/RepoHerd">
+    <link rel="canonical" href="https://ls-instruments.github.io/RepoHerd/">
+    <link rel="sitemap" type="application/xml" href="/RepoHerd/sitemap.xml">
     <style>
         :root {
             --bg: #0d1117;

robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://ls-instruments.github.io/RepoHerd/sitemap.xml

sitemap.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+  <url>
+    <loc>https://ls-instruments.github.io/RepoHerd/</loc>
+    <changefreq>monthly</changefreq>
+    <priority>1.0</priority>
+  </url>
+</urlset>