Set up action to validate TOML files

.github/workflows/validate.yml

@@ -0,0 +1,42 @@
+name: Validate data files
+
+on:
+  push:
+    paths:
+      - 'data/**/*.toml'
+
+  pull_request:
+    paths:
+      - 'data/**/*.toml'
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Setup cache for Taplo CLI executable
+        id: cache-taplo
+        uses: actions/cache@v4
+        with:
+          path: /usr/local/bin/taplo
+          key: taplo-0.8.1
+
+      - name: Install Taplo CLI
+        if: steps.cache-taplo.outputs.cache-hit != 'true'
+        run: |
+          wget -q -O - 'https://github.com/tamasfe/taplo/releases/download/0.8.1/taplo-linux-x86_64.gz' | gunzip -c > /usr/local/bin/taplo
+          chmod u+x /usr/local/bin/taplo
+
+      - name: Validate party series TOML file
+        run: taplo check data/series.toml && taplo format --check data/series.toml
+
+      - name: Validate party TOML files
+        run: |
+          shopt -s globstar
+          taplo check data/parties/**/*.toml && taplo format --check data/parties/**/*.toml