Is your feature request related to a problem? Please describe.
Right now, when we load the app, the loading screen starts with the default theme instead of the custom theme.

Describe the solution you'd like
What i expect is to actually have the app load with the custom theme so that the user experience feels smooth.

Describe alternatives you've considered
Maybe try to push the css to local storage and use use it as the default one right at the start of the app then fallback on the logseq theme if the custom theme isn't set.

Additional context
When there's a custom theme update, logseq should treat that file the same way as the md files, so any change should be merged with the local file.