add right-to-left layout support

**Is your feature request related to a problem? Please describe.**

Languages like Arabic, Persian, Hebrew, require right-to-left support for the admin layout.

**Describe the solution you'd like**

Enable right-to-left for the admin panel. This could be done:

1. Via configuration so that it is always enabled. This could work well if the site is uni-lingual and the layout can be pre-determined to be right-to-left.
2. Via a button on the admin panel that can switch the layout on demand. This is good for multi-lingual sites like English and Arabic which is common.
3. Per collection so the user can define collections that are right-to-left which will also work well for multi-lingual sites.

I guess we can start with #1 and then increase the complexity of the support afterwards.

**Describe alternatives you've considered**

I tried putting dir="rtl" in the root html element of the admin page. but it didn't work well (see the screenshot below).

**Additional context**