[web] Introduce edit link modal

Summary:
Introduce a stage of manage link modal where a link can be modified / created.

https://www.figma.com/file/a1nkbWgbgjRlrOY9LVurTz/Comm-%2F-Desktop-app?node-id=11341%3A281468&mode=dev

Depends on D8414

Test Plan: Check if edit link and enable link buttons point to edit link modal. Check if the modal is displayed correctly.

Reviewers: kamil, inka, bartek, ashoat

Reviewed By: ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D8415