feat: basic rtos task api

[ForsakenHarmony]

"threads" without std

I'm not entirely sure if just stopping them is ok, the vTaskDelte docs mention having to free task memory prior to stopping the task

depends on #13

[ivmarkov]

See my comments in #20
If we abstract away the spawning of a thread with a trait, then we would not need this.

[ivmarkov]

Closing. Main argument is as follows: using no_std on top of ESP IDF remains to be a solution looking for a problem, really.
Yet - while we still do that for the moment, exposing another thread API (FreeRTOS) in a Rust-safe way (as opposed to just using the unsafe esp-idf-sys bindings), seems to be going too far. Why would we do that?