Right side "sidebar handle" button is not noticeable

[MAX-786]

Describe the bug
The right side sidebar handle, people had issues and didn't know how to open and close it. What's worse (for new Volto editors), once you close the sidebar, it stays closed and the whole thing is lacking contrast and you won't know how to open it. It's a major UX problem.

To Reproduce
Steps to reproduce the behavior:

1. Open Volto Editor, and click on any block.
2. On the right side, the sidebar handle button is not visible clearly.
3. If you click on it and close the sidebar, it will remain closed.

Expected behavior
The sidebar handle button should be more opaque so it can be easily noticeable. And also it should open again when you click on any block.

Screenshots

Untitled.video.-.Made.with.Clipchamp.4.mp4

Software (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Volto Version [e.g. 8.5.0]
• Plone Version [e.g. 5.2.2]
• Plone REST API Version [e.g. 7.0.1]

[JeffersonBledsoe]

Related issue #3910 with a WIP PR to resolve it #3912 . More than happy for somebody to finish the PR off if they wanted :)

[prithvi009]

hey! @MAX-786 can I work on this issue?

[stevepiercy]

@prithvi009 in the Plone organization, you may pick up any open issue or PR, assign yourself to it (Assignees in the upper right corner of GitHub), and work on it. There is no need to ask, unless someone else is actively working on it.

See https://6.docs.plone.org/volto/developer-guidelines/index.html for details.

And welcome to Plone! We're a friendly bunch.

[MAX-786]

@prithvi009 Sure! as Steve already said, but u may have noticed this that we already have this related issue #3910 and WIP PR #3912. Feel free to look into it and work on it if u like :) .