Store bookmark data in the video's .metadata file

[lulzsun]

Relating to #34

We are currently storing bookmark data in localStorage instead of using the .metadata that is created in the relative .thumbs folder.

Currently, the .metadata file is storing the duration of the video.

[sshcrack]

Thinking about this issue. What would be the best way to implement

1. Reading the Metadata of the corresponding video and sending it to frontend
2. Save the bookmarks the user made

Maybe some kind of Event Sytem with React Hooks? Something like useBackendData which then handles retrieving information from the backend and storing it on change?

And some kind of shared message data payload types, so maybe basic c# structs get translated to typescript types?