RTLCSS
------

Import git ref: v1.0.1

Downloaded from: https://github.com/moodlehq/rtlcss-php

Import procedure:

- Copy all the files from the folder 'src/MoodleHQ/RTLCSS/' in this directory.
- Copy the license file.
- Re-apply Totara modifications

Totara changes:
  * TL-27760 - Fix CSS variables ending in left or right being renamed
  * TL-39996 - Upgrade RTLCSS to v1.0.1
