chore: add release PR flow (#130)

Author: erezrokah

.github/workflows/release-please.yml

@@ -0,0 +1,14 @@
+name: release-please
+on:
+  push:
+    branches:
+      - master
+jobs:
+  release-please:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: GoogleCloudPlatform/release-please-action@v2
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          release-type: node
+          package-name: '@netlify/plugin-lighthouse'

CONTRIBUTING.md

@@ -1,5 +1,7 @@
 # Contributing
 
+## Setup
+
 First fork this project
 
 ```bash
@@ -16,3 +18,10 @@ git push origin my-fix
 ```
 
 Lastly, open a pull request on Github.
+
+## Releasing
+
+1. Merge the release PR
+2. Switch to the default branch `git checkout master`
+3. Pull latest changes `git pull`
+4. Publish the package `npm publish`