Update note graph and reference list when new notes are created

[jevakallio]

This PR aims to fix the long standing issue where link reference definitions are not being generated for newly created files

Combined with the following changes in Markdown Links, this should make the editing experience a lot more fluid:

• Automatically update graph when new files are added tchayen/markdown-links#34 (update graph when new files are added)
• fix refresh of the graph tchayen/markdown-links#37 (keep graph visually stable when updating)

Changes

• Add notes to NoteGraph when they are created
• Trigger events from NoteGraph to notify listeners about added/updated notes
• Update reference definitions in active editor when new note is added

Behaviour

• New documents are indexed into the NoteGraph immediately, so linking to them from any document works immediately. Previously, you had to go to the newly created document and save it to get it to be registered.
• When the new file is created using Cmd+Click or just Cmd+Hover, the link is added to the "source" document immediately.
• When the new file is created using "Go to definition" (F12), the link is only added the next time you go back to the "source" document and save it.
  • This is because VS Code does not allow changing the content in non-active editors, so when the new file is generated and the editor is switched immediately
  • To fix this, we'd need to be able to capture the RevealDefinition action before it happens and pre-emptively create the reference before the file exists. The action is defined in Markdown Notes extension, which is out of scope for this PR
  • Another alternative would be to run the new Janitor command (WIP Implement janitor command to extension #155), but there's still a few kinks to be ironed out
  • For the time being, you can work around using the Cmd+Hover trick before navigating to the file

Demo

[jsjoeio]

LGTM! Super readable. Nice work @jevakallio ! 🌮