🔨 Add fix script

When linting during CI, misformatted code should result in a warning
instead of automatically getting fixed.

CONTRIBUTING.md

@@ -35,7 +35,7 @@ Thank you for considering contributing to Etro! There are many ways you can cont
   - Briefly review the images in **spec/integration/assets/effect/**
 - As you work, you can run
   ```
-  npm run lint
+  npm run fix
   npm run build
   npm test
   ```

package.json

@@ -55,9 +55,10 @@
     "prepare": "husky install",
     "effects": "node scripts/effect/save-effect-samples.js",
     "lint": "npm run --silent lint:main && npm run --silent lint:test && npm run --silent lint:examples",
-    "lint:main": "eslint -c eslint.typescript-conf.js --ext .ts --fix src",
-    "lint:test": "eslint -c eslint.test-conf.js --ext .ts --fix spec",
-    "lint:examples": "eslint -c eslint.example-conf.js --ext .html --fix examples",
+    "fix": "npm run --silent lint:main -- --fix && npm run --silent lint:test -- --fix && npm run --silent lint:examples -- --fix",
+    "lint:main": "eslint -c eslint.typescript-conf.js --ext .ts src",
+    "lint:test": "eslint -c eslint.test-conf.js --ext .ts spec",
+    "lint:examples": "eslint -c eslint.example-conf.js --ext .html examples",
     "start": "http-server",
     "test": "karma start",
     "release": "shipjs prepare"