Add CI workflow to validate configuration files against JSON schema

.github/workflows/check-configs.yml

@@ -0,0 +1,36 @@
+name: Check Configuration Files
+
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    paths:
+      - ".github/workflows/check-configs.yml"
+      - "Taskfile.ya?ml"
+      - "**/dependabot.ya?ml"
+  pull_request:
+    paths:
+      - ".github/workflows/check-configs.yml"
+      - "Taskfile.ya?ml"
+      - "**/dependabot.ya?ml"
+  schedule:
+    # Run every Tuesday at 8 AM UTC to catch breakage resulting from changes to the JSON schema.
+    - cron: "0 8 * * TUE"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/setup-task@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Validate configuration files
+        run: task config:validate

README.md

@@ -1,5 +1,6 @@
 # Tooling Project Assets
 
+[![Check Configuration Files status](https://github.com/arduino/tooling-project-assets/actions/workflows/check-configuration-files.yml/badge.svg)](https://github.com/arduino/tooling-project-assets/actions/workflows/check-configuration-files.yml)
 [![Check License status](https://github.com/arduino/tooling-project-assets/actions/workflows/check-license.yml/badge.svg)](https://github.com/arduino/tooling-project-assets/actions/workflows/check-license.yml)
 [![Check File Duplicates Sync status](https://github.com/arduino/tooling-project-assets/actions/workflows/check-sync.yml/badge.svg)](https://github.com/arduino/tooling-project-assets/actions/workflows/check-sync.yml)
 

Taskfile.yml

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+version: "3"
+
+tasks:
+  check:
+    desc: Check for problems with the project
+    deps:
+      - task: config:validate
+
+  config:validate:
+    desc: Validate configuration files against their JSON schema
+    vars:
+      # Last version with support for draft-04, used by Dependabot schema
+      AJV_CLI_VERSION: 3.3.0
+      # Source: https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/dependabot-2.0.json
+      DEPENDABOT_SCHEMA_URL: https://json.schemastore.org/dependabot-2.0
+      DEPENDABOT_SCHEMA_PATH:
+        sh: mktemp -t dependabot-schema-XXXXXXXXXX.json
+      DEPENDABOT_DATA_PATH: "**/dependabot.yml"
+    cmds:
+      - wget --quiet --output-document="{{.DEPENDABOT_SCHEMA_PATH}}" {{.DEPENDABOT_SCHEMA_URL}}
+      - npx ajv-cli@{{.AJV_CLI_VERSION}} validate -s "{{.DEPENDABOT_SCHEMA_PATH}}" -d "{{.DEPENDABOT_DATA_PATH}}"