ci: add release-please automation

- Add release-please workflow for automated releases

- Add release-please config (conventional commits, Go project)

- Initialize manifest at version 2.0.0 to indicate fork divergence

Author: James Ainslie

.github/workflows/release-please.yml

@@ -0,0 +1,21 @@
+name: Release Please
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  release-please:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: googleapis/release-please-action@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          config-file: .release-please-config.json
+          manifest-file: .release-please-manifest.json
+

.release-please-config.json

@@ -0,0 +1,46 @@
+{
+    "$schema": "https://raw.githubusercontent.com/googleapis/release-please/main/schemas/config.json",
+    "packages": {
+        ".": {
+            "release-type": "go",
+            "package-name": "staff",
+            "bump-minor-pre-major": true,
+            "bump-patch-for-minor-pre-major": true,
+            "changelog-sections": [
+                {
+                    "type": "feat",
+                    "section": "Features"
+                },
+                {
+                    "type": "fix",
+                    "section": "Bug Fixes"
+                },
+                {
+                    "type": "perf",
+                    "section": "Performance Improvements"
+                },
+                {
+                    "type": "refactor",
+                    "section": "Code Refactoring"
+                },
+                {
+                    "type": "docs",
+                    "section": "Documentation"
+                },
+                {
+                    "type": "test",
+                    "section": "Tests",
+                    "hidden": false
+                },
+                {
+                    "type": "build",
+                    "section": "Build System"
+                },
+                {
+                    "type": "ci",
+                    "section": "Continuous Integration"
+                }
+            ]
+        }
+    }
+}

.release-please-manifest.json

@@ -0,0 +1,3 @@
+{
+  ".": "2.0.0"
+}