Added all default widgets to documentation

[kyonlee]

Reasons for making this change

Added all the default widgets that can be overwritten in alphabetical order to documentation. Please review, and let me know if anything else is required for this issue. Fixes #1198

Checklist

• [o] I'm updating documentation
  • [o] I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[epicfaace]

Thanks!