chore: add lint.yml to run ESLint in CI (#47)

Author: JoshuaKGoldberg

.github/actions/prepare/action.yml

@@ -4,7 +4,6 @@ description: Prepares the repo for a typical CI job
 runs:
   using: "composite"
   steps:
-    - uses: actions/checkout@v3
     - uses: actions/setup-node@v3
       with:
         node-version: "18"

.github/workflows/lint.yml

@@ -0,0 +1,15 @@
+name: Lint
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ./.github/actions/prepare
+      - run: yarn lint