Non-firefox / Chromium-based browsers get disconnect message from WebSocket

[TheJoshue]

Title explains what happens.

Steps to reproduce:

1. execute /lp(b) editor on server
2. open given url in any Chromium-based browsers (i recommend testing with Brave or Google Chrome as those are the ones i can confirm this happens)
3. do not focus on/interact with tab where you opened the given LP editor url
4. wait like mentioned in step 3. for 5+- minutes
5. go to your LP editor url and you will see that "Apply" button became "Save" button
6. you can check console output by pressing F12 on that page, it should be something like this:
   

• This is not the case with Firefox browsers.

[lucko]

Should be fixed - I've tested using Chrome on macos, it now stays connected when the tab is in the background for ~5 mins. Should in theory stay open indefinitely now (providing the server is running and the user who created the session hasn't logged out).