Update test suite

[juliandsg0222]

Description

This PR resolves #274. The changes made were:

• Implemented mocks for the jsondiffpatch, jsondiffpatch/formatters/jsonpatch, and json-joy/lib/json-patch libraries.
• Created the startDocument, createDefaultBlock, and setFocus functions in the testHelpers file to mock the editor DOM.
• Updated the render, getCurrentBlockIndex, and getBlockByIndex methods in the editor mock.
• Updated and added tests for:
  1. Custom debounce timer provided.
  2. Operations without changes.
  3. Operations with one change.
  4. Operations with two changes.
  5. Undo/redo events fired with default shortcuts.
  6. Undo/redo events fired with custom shortcuts.
• Updated the getPosition method for standardizing the use of the getSelection function (changed document to window).
• Updated the bundle file.