Add presenter overlay when sharing screen

[DorraJaouad]

☑️ Resolves

• Fix Screensharing view does not show speaker #4478
• You can hide and unhide by clicking on the presenter overlay
• When hidden, a button will be shown.
• If the video is disabled from the stripe, the presenter overlay will be hidden. Pressing on the presenter button will enable the video and show the overlay.

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Default	🏡 On hover	🏡 Clicked	🏡 Stripe Open

🚧 Tasks

• Design/icons review
• Code review

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[Antreesy]

Looks cool code-wise and running! Nothing blocking from me.
Left some minor comments for improvements, and waiting for design team for decision

[Antreesy]

Left some nitpick comments

[jancborchardt]

Very cool! :) @DorraJaouad only a very small adjustment: To make the hide icon more symmetric with the one to show the video, instead of the "eye" I'd propose account-off: https://pictogrammers.com/library/mdi/icon/account-off/

[nickvergessen]

So, good to merge?

[jancborchardt]

Looks great! :)