Add ability to switch mobtime instance

[JStruk]

Currently, when the IDE is opened and the plugin loads, it shows the homepage for https://mobti.me. The user can enter a URL here, which will then direct them to that mobtimer. (i.e. the user types "abc123" and the mobtimer at https://mobti.me/abc123 will be displayed). We want to allow the user to switch to a different timer as they wish.

AC:

• Add a textbox at the top to allow the user to enter a different mobtime URL.
  • The text pulled from this should be appended to the URL: "https://mobti.me/{text-from-textbox}"
  • This allows the user to choose another mobtime instance but doesn't allow them to navigate away from the mobtime app
  • Should this be collapsable? Might look prettier
• Add a button to handle the timer change
  • Redirect the chromium browser to the new mobtime link