[doc] build instructions should be improved

[mkwork]

• Dependencies list missed (only platform depended requirements presented)
• Which Qt version it's depends on? Or list of supported versions
• How to perform build? Build instructions itself are missed.
• link to build instructions from README.md

[mkwork]

Quite informative hint: if there to hard to write build instructions, build system should be improved :)
Please review their or their build instructions as reference. Or somebody's using qmake documentation.

[Allexin]

building app is easy, but now i do not have clear view how to write this information correctly.
Thanks for references, it's very helpful

[danbelov]

I want to improve it, and i've created a pull request for that. If you accept it, i will try to improve it when i build it myself