Enable eslint (#1394)

Author: benmccann

.eslintignore

@@ -0,0 +1,8 @@
+**/_actual.js
+**/expected.js
+_output
+test/*/samples/*/output.js
+node_modules
+__sapper__
+/runtime/app.mjs
+/runtime/server.mjs

.eslintrc.js

@@ -0,0 +1,4 @@
+module.exports = {
+	root: true,
+	extends: '@sveltejs'
+};

.github/workflows/ci.yml

@@ -17,10 +17,9 @@ jobs:
     - run: npm test
       env:
         CI: true
- # Uncomment with https://github.com/sveltejs/sapper/pull/1198
-#  Lint:
-#    runs-on: ubuntu-latest
-#    steps:
-#    - uses: actions/checkout@v2
-#    - uses: actions/setup-node@v1
-#    - run: 'npm i && npm run lint'
+  Lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+    - run: 'npm i && npm run lint'