Document config options for CSAF provider

[tschmidtb51]

The CSAF provider comes with many options. They should be documented (including their default value) and explained.

[tschmidtb51]

https://github.com/csaf-poc/csaf_distribution/blob/44cd02bdc2b953bc825f6d0c674dcd07005fc687/cmd/csaf_provider/config.go#L152

I suggest to also use Example here instead of ACME.

 Name:      func(s string) *string { return &s }("Example"),

[tschmidtb51]

@bernhardreiter I just had to re-open that as it was not completed.

[bernhardreiter]

@tschmidtb51 merged, because it seems to fit your suggested use better. (We had asked back on the "ACME" example, see #40 (comment), this is why I've thought we were already good enough here.) Thanks for doing your suggestion directly as pullrequest.