docs: Document recipe on how to use RTL support

[MartinCupela]

Motivation Changes brought by theming v2 include RTL support. Users that would like to make use of this fact would need to create their own Stream18n instance and set the [dir="rtl"] attribute on a top level element. This recipe could facilitate their efforts. Also it would make the users aware of RTL being supported.

Proposed solution Create a small example of a top level React component that instantiates Streami18n object and sets the dir attribute on the top level element passing the i18n instance to the child Chat component. The example can be part of the customization/translations.mdx document for now.