Add GitHub Action for Markdown linting.

Author: Potherca

.github/workflows/linting.yml

@@ -20,6 +20,14 @@ jobs:
       - uses: actions/checkout@v2
       - uses: pipeline-components/php-linter@master
 
+  lint-markdown:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: pipeline-components/remark-lint@master
+        with:
+          args: remark --rc-path=build/.remarkrc --ignore-pattern='*/vendor/*' .
+
   lint-yaml:
     runs-on: ubuntu-20.04
     steps:

build/.remarkrc

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "remark-preset-lint-recommended",
+    ["remark-lint-list-item-indent", "space"]
+  ]
+}