doc: Enable all features

[chrysn]

So far, there has been one chip for which all major features were usable (nrf52840), and thus the riot-wrappers could be documented based on that one. With #36 (DAC), this is no longer the case.

How can we build documentation that covers all features without having such a chip?

[chrysn]

(This could also have been reported against https://gitlab.com/etonomy/riot-doc-helpers -- but a possible resolution is to replace that).

[Remmirad]

I am not quite sure I understand the problem, but I tried to setup a little RIOT module e.g. generate (target: native), added all needed modules to its Makefile (grep'ed them from lib.rs), and then setup this crates .cargo/config.toml with something like this here:

[env]
RIOT_COMPILE_COMMANDS_JSON = "generated/compile_commands.json"
RIOT_USEMODULE = "all modules as obtained from riot compile output"
[build]
target = "native target"

This way I then could use cargo doc -F "features" to build the documentation that seems to include all specified modules.