Theming improvements

[cyrneko]

Heya!

I've found this project recently, and I must say you all have done quite a nice job so far!

so I've been looking around the UI and would like to point out some things that I'd love to see added :)

Automatic Dark/Light theming based on OS/Browser Preference

Achievable through JavaSctipt on Browsers, not sure about Electron tbh lol, probably same there

in extension to this ↑↑↑ - Custom Dark/Light themes

Similar to Telegram, we could set Light/Dark themes which would be used by default when hitting the Light/Dark toggles or Auto-Switching

More keyboard shortcuts for various actions

notably for Markdown formatting, for example CTRL+I for italic, CTRL+B for bold, CTRL+E/CTRL+SHIFT+M for Monospace, and so on
in addition to keyboard shortcuts, having a context menu for selected text to do basically the same thing would also be nice

a manual reconnect button

next to the "You're offline" text to attempt a reconnection to the service for when it doesn't happen automatically (you might as well just trigger re-loading the tab)

Multi-Account switching

preferably also with configurable keyboard shortcuts, one to bring up a selector, and ones with numbers to switch to specific accounts quickly, for instance ALT+1/2/3...