Add share via Tokodon support
This adds a new Purpose plugin (the share url type) that allows you share information from other applications, into a new post!
There are two scenarios where this can happen:
Tokodon is already open
If Tokodon is open already, then the main window will activate and the status composer will open. This is an old recording, but it's about what it looks like:
Tokodon isn't open
If Tokodon isn't open, a new standalone composer opens up. If no accounts are available, it will show a relevant message - but it's not much more complex than that.
Notes
- Currently the share text is the title of the URL (if given) and the URL. The text can be further edited by the user, if they desire.
- Please keep in mind while testing that mixing KWindowSystem versions (which is easy to do when testing) will result in Tokodon crashing when you try to activate the window.
- You can't tell which account you're posting from in the status composer, but that's out of the scope of this MR and I'll be adding that in another one. It should be your default account though.