Add information on which features are provided by each board

[FlapKap]

Description

The process to find the features a board support is currently to have an application Makefile and call make BOARD=<board> info-features-provided. This is cumbersome for users looking for boards that support the features they want or even for developers looking for boards with a mismatch between the hardware they provide and the features they implement.

Ideally each board in the documentation would have a section on supported features and the "supported boards" section could have a table of boards and features

[chrysn]

There's some work in https://github.com/RIOT-OS/RIOT/pull/20395 on this; adding some screenshots there.