Add debug watch window to the script editor

[ambrosiogabe]

When you're debugging a luau script, you should be able to inspect variables through a debug window (or by hovering the mouse over the variable). This issue should implement:

• A watch window where you can type a variable name in and inspect it's contents
  • The variable should be displayed as a JSON struct in the watch window with collapsible arrows for different sub-properties
• When you hover a variable, a mini content displayer should show you what the variable contents are under the mouse cursor
  • This should use the same content window as the inspector window for consistency