Add base rtl support

[hellcp]

This does look a touch broken, but it's a big improvement for those that need it:

html[lang^=ar] body,
html[lang^=he] body,
html[lang^=sy] body,
html[lang^=sam] body,
html[lang^=men] body,
html[lang^=man] body,
html[lang^=wo] body,
html[lang^=ff] body {
 direction:rtl;
 text-align: right;
}

[guoyunhe]

It is said that Bootstrap 5.0 will solve RTL issues. https://getbootstrap.com/docs/5.0/getting-started/rtl/

[hellcp]

We do already get complaints about missing rtl support in get.o.o though, and that is gonna be a problem for www.o.o as well