Hide "Regular speed" controls by default

[WofWca]

Specifically, hide them when the "Whenever playback rate gets changed by other scripts" is set to "I want to control playback rate (sounded speed) through the website's UI or through other extensions, not just this one. This will update sounded speed whenever playback rate gets changed".

And add an option to still show them.

Why

It simplifies the UI, which reduces confusion. Makes people understand that they can still control playback rate through the website even with this extension installed.

Additional info

Need to think about shortcuts that change the "regular speed"