docs: prepare repository for GitHub contributors

Signed-off-by: Magnus Hedemark <magnus919@pm.me>

.github/workflows/validate.yml

@@ -0,0 +1,22 @@
+name: Validate skills
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.3'
+      - name: Validate skill format and links
+        run: ruby scripts/validate-skills.rb