🚧 Feedback modal UI 🚧 (#3536)

[[PR Description]]

TODO: 
- [x] Add placeholder text to editor
- [x] Add external link icon to "Community repo" button
- [x] Show `not-allowed` cursor for disabled buttons
- [ ] Add `Headline` ui component
- [ ] Finish UI pass
- [ ] Fix `IconPosition` on button (should swap the icon side)
- [ ] Add conditional tooltip for disabled "Send feedback" button.
- [ ] Add common/top feedback link.
- [ ] Add `vw`/`vh` units to allow sizing the modal based on viewport
size.

Release Notes:

- N/A