Add setting to change the position of the button that toggle on Front End Highlighting

[amberhinds]

There are issues with many websites where our Front End Highlighting button covers other fixed position buttons (chat modals, theme controls, etc.).

This is just one example:

Let's add a setting.

Front-end Accessibility Checker button position:

• Bottom right corner (default)
• Bottom left corner
• Admin bar

This is sort of medium-high because I'm seeing more reports of this.