Adding Chat topic

[gedinakova]

Closes #

Checklist:

• [ ] check topic's TOC/menu and paragraph headings
• [ ] Include TOC topic labels in topic content has a valuable update, it's new or considered as preview\ beta
• [ ] link to other topics using ../relative/path.md
• [ ] at the References section at the end of the topic add links to topics, samples, etc
• [ ] reference API documentation instead of adding a section with API

• [ ] use valid component names - [Data] Grid, IgxSelectComponent, <igx-combo>
• [ ] use spell checker tool (VS Code, Grammarly, Microsoft Editor)
• [ ] add inline code blocks for the names of classes / tags / properties
• [ ] add language descriptor for the code blocks
• [ ] check broken links (use browser add-on)
• [ ] check if sample is working and fully visible in the topic
• [ ] check if sample is working and fully visible in the StackBlitz
• [ ] check if code blocks match the code in StackBlitz demo

• [ ] follow SEO guidelines to fill topic's metadata (SEO guidelines)

• [ ] do not resolve requested changes (leave that to the reviewer)
• [ ] add pending-localization label when the review of the PR is done
• [ ] add a member from the localization team to translate it