feat: add a GitHub action to lint the YAML files

Lint some YAML
Add a `.yamllint` config file

.github/workflows/lint.yml

@@ -0,0 +1,12 @@
+name: ❄️ Lint
+
+on: [pull_request]
+
+jobs:
+  yamllint:
+    name: 🍺 YAML
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: 🧹 YAML Lint
+        uses: ibiqlik/action-yamllint@v3

.yamllint

@@ -0,0 +1,8 @@
+---
+
+extends: default
+
+rules:
+  document-start: disable
+  line-length: disable
+  truthy: disable