2.5.4

Release 2.5.4

- Adds new Extension API allowing folks to define their own routes
  and API functionality via separate Obsidian Plugins.
  - Want to expose REST API routes as part of your existing plugin?  Now
    you can!
  - Need an API feature that doesn't quite fit the scope of what
    Obsidian Local REST API intends to provide?
    Now you can add your own routes in your own plugin,
    but let them be served by Obsidian Local REST API.