ci: add linter workflow

.github/workflows/linter.yml

@@ -0,0 +1,22 @@
+name: Lint
+
+on: [pull_request]
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Lint Code Base
+        uses: github/super-linter@v3
+        env:
+          VALIDATE_ALL_CODEBASE: false
+          DEFAULT_BRANCH: v3.x
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          FILTER_REGEX_INCLUDE: .*src/.*

README.md

@@ -1,8 +1,9 @@
 # GitHub Slug action
 
 [![Actions Status][1]][2]
+![GitHub Super-Linter][13]
 [![Public workflows that use this action.][8]][9]
-[![Licence][11]][10]
+[![Licence][11]][12]
 
 This GitHub Action will expose the slug value of all [GitHub environment variables][10] inside your GitHub workflow.
 
@@ -148,3 +149,4 @@ Please, use the current branch `v3.x` or a version tag (see [releases pages][6])
 [10]: https://docs.github.com/en/free-pro-team@latest/actions/reference/environment-variables#default-environment-variables
 [11]: https://img.shields.io/github/license/rlespinasse/github-slug-action
 [12]: https://github.com/rlespinasse/github-slug-action/blob/v3.x/LICENSE
+[13]: https://github.com/rlespinasse/github-slug-action/workflows/Lint/badge.svg