ci: add explicit permissions to github workflows

- Add `contents: read` and `pull-requests: write` permissions to analyze
  workflow
- Add `contents: read` permission to backup workflow
- Add `contents: write` permission to publish workflow
- Add `contents: read` permission to test workflow

Author: tsinis

.github/workflows/analyze.yaml

@@ -11,6 +11,10 @@ on:
       - "pubspec.yaml"
       - ".github/workflows/analyze.yaml"
 
+permissions:
+  contents: read
+  pull-requests: write
+
 jobs:
   analysis:
     name: 🕵️ Analyze

.github/workflows/backup.yaml

@@ -5,6 +5,9 @@ on:
     branches:
       - main
 
+permissions:
+  contents: read
+
 jobs:
   mirror-to-gitlab:
     name: 💾 Backup to GitLab

.github/workflows/publish.yaml

@@ -12,6 +12,9 @@ on:
     tags:
       - "[1-9]+.[0-9]+.[0-9]+*"
 
+permissions:
+  contents: write
+
 jobs:
   publish-dry-run:
     name: 📝 Publish dry run

.github/workflows/test.yaml

@@ -20,6 +20,9 @@ on:
       - "pubspec.yaml"
       - ".github/workflows/test.yaml"
 
+permissions:
+  contents: read
+
 jobs:
   test:
     name: 🧪 Test