Add labeller action

Automatically label PRs based on the first part of the branch name:

fix/ -> bug
feat/ -> enhancement
maint/ -> maintenance
doc/ -> documentation
depr/ -> deprecation
test/ -> test

.github/labeler.yml

@@ -0,0 +1,17 @@
+bug:
+  - head-branch: ['^fix/']
+
+enhancement:
+  - head-branch: ['^feat/']
+
+maintenance:
+  - head-branch: ['^maint/']
+
+documentation:
+  - head-branch: ['^doc/']
+
+deprecation:
+  - head-branch: ['^depr/']
+
+test:
+  - head-branch: ['^test/']

.github/workflows/labeler.yml

@@ -0,0 +1,13 @@
+name: Label pull requests
+
+on:
+  - pull_request_target
+
+jobs:
+  labeller:
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/labeler@v5