Idea: Rename repo to reflect multiple supported chips

[jekader]

The project repo is currently called OpenBK7231T_App yet the firmware is ported to many more platforms than just BK7231T.

Personally, I have trouble locating the repo so I google "openbeken" to find what I need. I also do not own any Beken hardware but still find the firmware very useful on other chips.

The proposal is to choose a more generic name like openbeken/obk/etc and use that to make the repo easier to find. Having a more recogniseable name not linked to a specific chip name sounds good for the future and community building in general.