Simplified eslint config

src/registerServiceWorker.js

@@ -1,3 +1,5 @@
+/* eslint-disable @typescript-eslint/promise-function-async, @typescript-eslint/no-misused-promises */
+
 // In production, we register a service worker to serve assets from local cache.
 
 // This lets the app load faster on subsequent visits in production, and gives
@@ -96,7 +98,7 @@ function checkValidServiceWorker(swUrl) {
       // Ensure service worker exists, and that we really are getting a JS file.
       if (
         response.status === NOT_FOUND_STATUS ||
-        response.headers.get('content-type').indexOf('javascript') === -1
+        response.headers.get('content-type').includes('javascript')
       ) {
         // No service worker found. Probably a different app. Reload the page.
         return navigator.serviceWorker.ready.then((registration) =>