Add UI text work to tech writing handbook and update Product Designer content
- Adds mention of UI text to main page
- Adds detail on how to collaborate on UI text on Workflows page
- Updates Product Designer page with further clarity and a link to detail in Technical Writing handbook
- Updates outdated process information as MVC for further edits
This content is still under /product/technical-writing while we complete multiple handbook MRs, and it will be moved to /engineering in a future MR.
Edited by Christie Lenneville