chore(ci): add automated publishing to pub dev on tag push (#45)

* chore(ci): add automated publishing to pub dev on tag push
* chore(ci): remove on branch protection
* chore: rm unnecessary dart language setup

.github/workflows/publish_pub_dev.yml

@@ -0,0 +1,26 @@
+name: Publish to pub.dev
+
+on:
+  push:
+    tags:
+      - "[0-9]+.[0-9]+.[0-9]+" # tag pattern on pub.dev: '{{version}'
+
+# Publish using custom workflow
+jobs:
+  publish:
+    permissions:
+      id-token: write # Required for authentication using OIDC
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          cache: true
+
+      - run: flutter doctor -v
+      - run: flutter pub get
+      - run: dart run build_runner build --delete-conflicting-outputs
+
+      - run: flutter pub publish --force