Feature: allow for plugins to reload dynamically

[elpoelma]

This PR includes the following features:

• The option for plugins to be dynamically reloaded: when changing the plugins array which is passed to the editor-component, a restart/rebuild of the app is no longer required.
• Introduction of some new dummy plugins: the editor now contains highlight, code-mark and inline-components dummy plugins.

Additionally, this PR also changes the interface of some classes:

• Registering widgets, marks and inline components now happen on the transaction-level. The corresponding methods are moved from the Controller to the Transaction class.

• The plugin initalize method signature has changed, it now also expects a transaction object:

  initialize(
   transaction: Transaction,
   controller: Controller,
   options: unknown
  )
  

• Plugins can now also implement an optional willDestroy method. This is useful to remove listeners which have been added in the initialize method.

  willDestroy(transaction: Transaction)