Add description and documentation link to modal

[adhityamamallan]

Summary

• Modify the config type to add fields for more detailed modal content, such as a more detailed explanation and a link to docs.
• Set autoFocus to true for the Modal button so that it is focused when the modal is opened (the default behaviour is to focus on the first interactive element, which in this case is the link)

Test plan

Updated unit tests + ran locally.

Action modals:

Testing focus: