Add intellisense to the luaua script editor

[ambrosiogabe]

This should add some simple intellisense to the script editor. This issue will be complete when:

• You press Ctrl+Dot it opens a suggestion window
  • These suggestions should be populated based off of in-scope functions, variables, and types
• If you type . after a variable, it should open a suggestion window that shows the available properties based on the type

Check out how TypeScript intellisense works in VSCode for some inspiration.