feat: introduce new help overlay for add section button

[dcshzj]

Problem

The add section button does not have the ability to show a help overlay.

Solution

Breaking Changes

• Yes - this PR contains breaking changes
• No - this PR is backwards compatible

Features:

• The add section button now has a new help overlay component, which allows a popover to appear on the right side of the option upon hover.
• The Editable component is also promoted to a shared component, and stories were added for the AddSectionButton to showcase the new help overlay.

Before & After Screenshots

BEFORE:

AFTER:

Tests

• Unit tests (using npm run tests)
• e2e tests (comment on this PR with the text !run e2e)
• Smoke tests
  • Run the storybook and navigate to components/AddSectionButton
  • Ensure that the help overlay appears for text cards, info-columns and announcements
  • Navigate to any site
  • Ensure that there are no regressions in the Editable functionality (dnd, accordion, etc) for homepage, contact us and navigation bar pages

Deploy Notes

None

[dcshzj]

!run chromatic

[dcshzj]

!run chromatic

[dcshzj]

@sehyunidaaa Chromatic review is here: https://www.chromatic.com/review?appId=61fcc8e14c3af9003a102ac9&number=1515&type=linked&view=changes

[kishore03109]

Approving since my comments are non-functional.
I do think think the storybook code can be made a lot neater for extensibility in the future

Biz logic wise lgtm

[kishore03109]

Hey, what are your thoughts on creating an object interface for each card, then passing in an array?
This way we can

1. easily extend in the future if needed
2. less verbose code
3. Guarantee each object has the same shape in one glance

[dcshzj]

Adjusted in b688a48! I think I got a little carried away here oops.