ci: add automated skill review for SKILL.md pull requests

Adds a lightweight GitHub Action that reviews any SKILL.md files changed
in a pull request using tessl skill review. Posts results as a PR comment
with minimal permissions (pull-requests: write, contents: read).

Signed-off-by: Alan Pope <alan@popey.com>

Author: popey

.github/workflows/skill-review.yml

@@ -0,0 +1,14 @@
+name: Skill Review
+on:
+  pull_request:
+    paths: ['**/SKILL.md']
+
+jobs:
+  review:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+      - uses: tesslio/skill-review@main