GhostText editor capabilities document

Not all editors behave the same. There should be a way to write how GhostText-compatible targets should behave. A partial list

## Server
- [x] The editor should start listening to connections as soon as it's opened
- [x] The editor should allow the configuration of the port
- [x] The editor should automatically restart the server when the port is changed
- [ ] The editor should throw an error/notification if it can't open the port

## On connection

- [ ] Create a new transient/temporary document so that when closing it the user isn't prompted to save it
- [ ] If there's a disconnected GhostText tab open, reuse it
- [ ] If there's a connected GhostText tab, create a new tab next to it
- [ ] If there aren't any other GhostText tab, create a new a *new* [transient workspace](https://code.visualstudio.com/updates/v1_58#_transient-workspaces)
- [ ] The document should gain focus and be brought to the top so that the user can immediately start writing

## Document

- [x] It should indicate that GhostText is active (via filename, status bar, etc) perhaps using 👻🌕 and 👻🌘 as indicators.
- [x] It should start as Markdown, but probably just let the editor automatically figure it out if it can

## Updates

- [ ] The updates should be throttled depending on the text length (between 50ms and 1s)

## Options

- [ ] Server port
- [ ] Gain focus on connection