Feature derive defmt for debug printing of enums

[wallem89]

To be able to print signals with an enum with no_std I added defmt to format the enum values so they can be printed for debugging right away. This is done with an optional flag to enable this feature.

[projectgus]

@wallem89 I saw your PR and remembered I implemented defmt support a couple of months back, too. 🤦

I've submitted it as #91. It's similar to yours but I also implemented Format for message structs.

[wallem89]

@wallem89 I saw your PR and remembered I implemented defmt support a couple of months back, too. 🤦

I've submitted it as #91. It's similar to yours but I also implemented Format for message structs.

Your PR works for me too. And i like the Format for the message structs. Let's get yours merged and into a next release!

[linusharberg]

#91 merged, closing this