Add about.rst on the main documentation page

[quillcraftsman]

Is your feature request related to a problem? Please describe.
Now about page is the part of menu on the main documentation page.
I propose to include it to the main page

Describe the solution you'd like

• use include to add about.rst on the main page.
  This is the example: find similar docs

Additional context

• If it possible find a way how to remove duplicates between readme.md and about.rst