Mounting of external systems into SB

Enables mounting of external folders or SB instances into your space.

Installation

Open your PLUGS note in SilverBullet and add this plug to the list:

- github:silverbulletmd/silverbullet-mount/mount.plug.json

Then run the Plugs: Update command and off you go!

Configuration

Create a MOUNTS page:

    ```yaml
    # Mounting another local folder with a docs/ prefix
    - prefix: docs/
      path: file:/Users/me/docs
    # Mounting an external SB instance to remote/
    - prefix: remote/
      path: http://some-ip:3000
      password: mypassword
    ```