Fails to parse FIT file with developer fields

[joelso]

Parsing fails when record contains developer defined fields which are used by third party app developers and new in FIT 2.0 (?) spec.

The parsing itself does not crash but data after such a message becomes jibberish.

I created a fork with a fix, tests are passing but still early in the process, will create a PR to main repo once stable.

If anyone wants to have a look, here it is:

https://github.com/FrostDigital/easy-fit/pull/1