Add WithFeaturesFS to use embedded feature files

[sagikazarmark]

Is your feature request related to a problem? Please describe.
GoBDD needs to read files from the filesystem at runtime which works, but could be better.

Describe the solution you'd like
Add a WithFeaturesFS funcion to use embedded feature files. This way files would be compiled into the test binary and tests would become more self-contained. Missing features would be noticed compile time.

Additional context
This isn't necessarily a great idea, but I had it and wanted to take a note. Maybe it's worth something.