Fix mentions in RTL
Summary
Ensure mentions are always displayed LTR, so the @ symbol is in the correct place.
Also add dir="ltr" to the body for non-RTL languages, so ltr:whatever Tailwind names can work. Tailwind docs recommend this:
Always set the direction, even if left-to-right is your default
https://tailwindcss.com/docs/hover-focus-and-other-states#rtl-support
Screenshots (if appropriate):
