Add eslint to Github workflows

We want this code to be well formatted even if it is just for automated
tests. To ensure this, run linting checks when opening pull requests.

PER-9318: Write healthcheck test (webclient functional test)

.github/workflows/lint-js.yml

@@ -0,0 +1,26 @@
+name: Lint (TypeScript)
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: "18"
+      - uses: actions/cache@v2
+        with:
+          path: node_modules
+          key: ${{ runner.os }}-node_modules-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node_modules-
+      - name: Move to JS directory
+        run: cd js
+      - name: Install dependencies
+        run: npm install
+      - name: Run eslint
+        run: npm run lint