Add guidance to useKLiveRegion doc page regarding the actionable element focus

[MisRob]

Follow-up to @radinamatic's feedback in learningequality/kolibri#12475:

[Mamatha1718]

Hi @MisRob , I would like to tackle this issue, will you please assign it to me and guide me where would i start to develop this documentation.
Thank you.

[MisRob]

Hi @Mamatha1718, thank you, I will assign you. Here's the guidance I usually post for documentation writing:

Guidance

• For consistency in documentation, first see the “Writing” guidelines and use existing pages for reference, such as the KTextbox documentation and KImg documentation pages.
• Generally we try to strike a balance between documenting all important modes of a component, while not overwhelming readers with unnecessary details or exhaustive lists of all possible states.
• Use simple, clear, and concise language. Think about whether what you are explaining can be easily understood by newcomers.
• To understand the technical aspects of writing documentation, refer to:
  • “How to update the documentation website”
  • Documentation pages code, such as KTextbox docs source code or KImg's docs source code

[MisRob]

@Mamatha1718 After you have run the development server (see the contributing guidelines) and familiarized yourself with the guidance above, you're welcome to post here if there are further questions