Make createWindow synchronous + grab first window on deeplink

[sergeichestakov]

Why

• createWindow doesn't need to be async (we don't need to block on setting the right bg color)
• We want the deeplink logic to match the behavior we use for grabbing the "last" window in the createWindow function: either the focused window, if one exists, or the first window we find if there are any open.

Main motivation is to prevent a redundant window from opening up when the app is opened via Deeplink (see Linear). e.g. if you open a replit://home link which launches the app you should see only one window with the home screen pop up not a home screen window and another window with your last Repl. Not sure if this fixes it but it's a good start to avoid race conditions between the onReady logic in main.ts and handling the first deeplink.

What changed

Make createWindow synchronous + grab 1st window on deeplink like we do when creating window.

Test plan

Deeplinks / creating windows should work as expected. The problem designed above is potentially fixed once packaged/released

[szymonkaliski]

nice!