Add github workflow for validation.

Author: simono

.github/dependabot.yml

@@ -9,3 +9,7 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/validate.yml

@@ -0,0 +1,24 @@
+name: Validate
+
+on: [push, pull_request]
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          submodules: true
+
+      - name: Validate Fish scripts
+        run: |
+          sudo apt update
+          sudo apt install -y fish
+          fish -n fish/**/*.fish
+
+      - name: Validate Dotbot configs
+        run: |
+          pip install dotbot
+          dotbot -n -c dotbot-config.yaml
+          dotbot -n -c dotbot-sync.yaml
+          dotbot -n -c dotbot-update.yaml