[l10n] Add support for right-to-left script languages

[tudoramariei]

Is your feature request related to a problem? Please describe.
Some languages (e.g., Arabic, Hebrew) have text written RL-TB (right-to-left, top-to-bottom) instead of the European LR-TB (left-to-right, top to bottom) (e.g., any Latin-letters language).
We currently have no support for these languages.

Describe the solution you'd like
When adding a new language to the admin interface, a new option should be available to account for the direction of writing, with the default being LR-TB (most already deployed websites use LR-TB).
Pages in these languages should display the text accordingly, with a right-page alignment.

Additional context
Additionally, support for TB-RL (top-to-bottom, right-to-left) would also be necessary at some point for languages such as Chinese, Japanese, and Korean.