Add publish action

Author: laurynas

.github/workflows/publish.yml

@@ -0,0 +1,13 @@
+name: Release to Packagist
+on:
+  release:
+    types: [published]
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Dispatch packagist update
+        run: |
+          curl -X POST https://packagist.org/api/update-package?username=${{ secrets.PACKAGIST_USERNAME }}&apiToken=${{ secrets.PACKAGIST_API_TOKEN }} \
+            -d '{"repository":{"url":"https://github.com/detectlanguage/detectlanguage-php"}}' \
+            -H "Content-Type: application/json"