Doc Features: Application shutdown

[pushker001]

Begin documenting application features with describing application shutdown.

• The title of my pull request is a short description of the changes
• This PR relates to some issue: relates to Document application capabilities #255

[undera]

Please save the screenshot into images directory and reference it from doc, instead of third-party location.

Also, care about readers and make sure your English is more or less correct. Use ChatGPT for help, if needed:

[undera]

Note how I changed the title and description of PR to match the meaning of the changes more precisely.

Also, about the screenshot: avoid too much drawing on it. Simple arrow is enough to point to object. Sometimes when you want to outline large block, use simple rectangle, not circle. Small objects don't need rectangles at all.

Overall, this PR goes into right direction now. Thank you!

Please address my comments above to finalize it.

[undera]

Thanks for the contribution! It's a good first step to document the application features.