chore: Automatically upgrade workflow dependencies (#48)

Configures Dependabot to automatically upgrade outdated workflow
dependencies, and adds automation for pull request labelling based on
commit message prefixes.

.github/dependabot.yaml

@@ -0,0 +1,18 @@
+version: 2
+
+updates:
+- package-ecosystem: github-actions
+  commit-message:
+    prefix: chore
+    prefix-development: chore
+  directory: "/"
+  labels:
+  - chore 🧹
+  - workflows 👷‍♀️
+  pull-request-branch-name:
+    separator: /
+  reviewers:
+  - unfunco
+  schedule:
+    day: sunday
+    interval: weekly

.github/labeler.yaml

@@ -0,0 +1,3 @@
+"workflows 👷‍♀️":
+- changed-files:
+  - any-glob-to-any-file: .github/**/*.yaml

.github/workflows/pr_label.yaml

@@ -0,0 +1,42 @@
+name: PR / Label
+
+on:
+  pull_request_target: { }
+
+jobs:
+  triage:
+    name: Triage
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+    - name: Apply context labels
+      uses: actions/labeler@v5
+      with:
+        configuration-path: .github/labeler.yaml
+        sync-labels: true
+    - name: Apply commit message labels
+      uses: actions/github-script@v7
+      with:
+        script: |
+          const labels = []
+          if (context.payload.pull_request.title.startsWith('fix:')) {
+            labels.push('bug 🐛')
+          }
+          if (context.payload.pull_request.title.startsWith('chore:')) {
+            labels.push('chore 🧹')
+          }
+          if (context.payload.pull_request.title.startsWith('feat:')) {
+            labels.push('feature 💡')
+          }
+          if (labels.length > 0) {
+            github.rest.issues.addLabels({
+              issue_number: context.issue.number,
+              labels,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+            })
+          }