Add GitHub Action for Yaml linting.

Author: Potherca

.github/workflows/linting.yml

@@ -19,3 +19,11 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: pipeline-components/php-linter@master
+
+  lint-yaml:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: "docker://pipelinecomponents/yamllint:latest"
+        with:
+          args: yamllint --config-file=build/.yamllint .

build/.yamllint

@@ -0,0 +1,14 @@
+---
+extends: default
+
+ignore: |
+  solid/vendor/
+
+rules:
+  brackets:
+    max-spaces-inside: 1
+  document-start: disable
+  line-length:
+    level: warning
+    max: 120
+  truthy: {allowed-values: ["true", "false", "on"]}