ci: add release-please for automated versioning and releases

Conventional commits on main will auto-create a release PR with
changelog and version bump. Merging the PR creates a GitHub release
which triggers the existing publish.yml NuGet workflow.

Author: rubenhensen

.github/workflows/release.yml

@@ -0,0 +1,23 @@
+name: Release
+
+on:
+  push:
+    branches:
+      - main
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
+jobs:
+  release-please:
+    name: Release Please
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: googleapis/release-please-action@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          release-type: simple
+          package-name: E4A.PostGuard

.release-please-manifest.json

@@ -0,0 +1,3 @@
+{
+  ".": "0.1.1"
+}

release-please-config.json

@@ -0,0 +1,17 @@
+{
+  "packages": {
+    ".": {
+      "release-type": "simple",
+      "package-name": "E4A.PostGuard",
+      "extra-files": [
+        {
+          "type": "xml",
+          "path": "src/E4A.PostGuard.csproj",
+          "xpath": "//Project/PropertyGroup/Version"
+        }
+      ],
+      "changelog-path": "CHANGELOG.md"
+    }
+  },
+  "$schema": "https://raw.githubusercontent.com/googleapis/release-please/main/schemas/config.json"
+}