feat: add reusable eslint action

Runs the eslint defined in the given package.json, configured by the associated eslint.config.mjs file.

.github/workflows/reusable-eslint.yml

@@ -0,0 +1,43 @@
+name: reusable eslint
+on:
+  workflow_call:
+    inputs:
+      paths:
+        required: true
+        type: string
+        description: |
+          A list of root directory/s to where a package.json and eslint
+          configuration file (eslint.config.mjs) exist.
+          e.g.: my/root/one my/cool/root/two
+jobs:
+  eslint:
+    runs-on: ubuntu-latest
+    steps:
+      - if: ${{ startsWith(github.repository, 'GeoNet/') == false }}
+        name: require GeoNet org
+        run: |
+          exit 1
+      - name: Parse paths
+        id: parse-paths
+        run: |
+          if [ -n "${{ inputs.paths }}" ]; then
+            echo "paths=$(echo '${{ inputs.paths }}' | tr '\n' ' ')" >> $GITHUB_OUTPUT
+          else
+            exit 1
+          fi
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+      - uses: actions/setup-node@60edb5dd545a775178f52524783378180af0d1f8 # v4.0.2
+        with:
+          node-version: '20.x'
+      - name: Install Node modules
+        id: install-node-modules
+        env:
+          PATHS: ${{ steps.parse-paths.outputs.paths }}
+        run: |
+          echo "$PATHS" | tr ' ' '\n' | xargs -i -n 1 npm install --prefix '{}'
+      - name: Run ESLint
+        id: eslint
+        env:
+          PATHS: ${{ steps.parse-paths.outputs.paths }}
+        run: |
+          echo "$PATHS" | tr ' ' '\n' | xargs -I '{}' -n 1 sh -c 'ESLINT_USE_FLAT_CONFIG=true $1/node_modules/.bin/eslint -c $1/eslint.config.mjs "$1"' _ '{}'

README.md

@@ -25,6 +25,7 @@
     - [Markdown lint](#markdown-lint)
     - [Copy to S3](#copy-to-s3)
     - [Clean container versions](#clean-container-versions)
+    - [ESLint](#eslint)
   - [Composite Actions](#composite-actions)
     - [Tagging](#tagging)
   - [Other documentation](#other-documentation)
@@ -1092,6 +1093,30 @@ jobs:
       number-kept: 7
 ```
 
+### ESLint
+
+STATUS: alpha
+
+Used to run ESLint on one or more directories. The paths specified
+should have a package.json with eslint defined, alongside an eslint config
+file named eslint.config.mjs.
+
+```yaml
+name: eslint
+on:
+  push: {}
+  pull_request: {}
+  workflow_dispatch: {}
+jobs:
+  eslint:
+    uses: GeoNet/Actions/.github/workflows/reusable-eslint.yml@main
+    with:
+      paths: |
+        ./root/folder/one
+        ./cool/root/folder/two
+```
+
+
 ## Composite Actions
 
 ### Tagging