Summary:
A new widget type Forms. For now hidden behind GRIST_EXPERIMENTAL_PLUGINS().
This diff contains all the core moving parts as a serves as a base to extend this functionality
further.
Test Plan: New test added
Reviewers: georgegevoian
Reviewed By: georgegevoian
Subscribers: paulfitz
Differential Revision: https://phab.getgrist.com/D4130
Summary: Added boilerplate code needed to create new wigets in "Add new" menu, that are wrapped around existing custom widgets. More details can be found here: https://grist.quip.com/larhAGRKyl6Z/Custom-widgets-in-Add-Widget-menu
Test Plan: nbowser tests added to verify if item in menu exits, if widget is rendered, and right side menu has widget selection and read access selection hided.
Reviewers: georgegevoian
Reviewed By: georgegevoian
Differential Revision: https://phab.getgrist.com/D3994
