Add a feature for logging panics with defmt about esp-backtrace

[bjoernQ]

I'm not too familiar with defmt to be honest. Probably error!() is more like dbg! from the std-lib, then?
Sounds like you probably only want one invocation of error! in your implementation

By "should I add this functionality to esp-println" you mean printing the source code location? I don't think we should do that for println but if you like you can add a dbg macro just like https://github.com/rust-lang/rust/blob/efa717bc2d82c19c6957f362a936a6f95169d138/library/std/src/macros.rs#L339-L361 to esp-println

Otherwise, happy to receive a PR for this

[TheButlah]

By "should I add this functionality to esp-println" you mean printing the source code location?

No, I meant should I add a print-defmt feature to esp-println. I'm not sure if its a good match because defmt introduces its own formatting by attaching line numbers and log levels to each print. See this example:

[jessebraham]

I'm just starting to learn defmt myself, but esp-println at least has support for it now. Maybe somebody can tackle this issue.

[bjoernQ]

I guess this is covered by #43