eslint: use cache (brianc#3218)

This significantly speeds up eslint after first run.

Co-authored-by: alxndrsn <alxndrsn>

Author: alxndrsn

.gitignore

@@ -7,5 +7,6 @@ package-lock.json
 *.swp
 dist
 .DS_Store
+/.eslintcache
 .vscode/
 manually-test-on-heroku.js

package.json

@@ -17,7 +17,7 @@
     "docs:start": "cd docs && yarn start",
     "pretest": "yarn build",
     "prepublish": "yarn build",
-    "lint": "eslint '*/**/*.{js,ts,tsx}'"
+    "lint": "eslint --cache '*/**/*.{js,ts,tsx}'"
   },
   "devDependencies": {
     "@typescript-eslint/eslint-plugin": "^7.0.0",