feat(Modal): support custom triggers

[stephenjwatkins]

📝 Changes

• Add <ModalContainer /> component to support custom triggers
• This follows the DialogContainer pattern from React Spectrum.
• Added a "versions" table to the Modal spec but didn't update the spec itself with the new types. Still unsure whether specs should be snapshots or living

✅ Checklist

• Code is complete and in accordance with our style guide
• Unit tests are written and passing
• TSDoc is written or updated for any component API surface area
• Stories in Storybook accompany any relevant component changes
• Ensure no accessibility violations are reported in Storybook
• Changeset is added
• Specs and documentation are up-to-date
• Cross-browser check is performed (Chrome, Safari, Firefox)

[ldewald]

Saw your comment on this. I'm not sure if it's too much info to be added as documentation in Storybook but might be cool to have them living and attached

[stephenjwatkins]

i agree. i'll think about how we could do that