Wrong docstring for nanocbor_put_bstr

[Timothy Claeys]

The docstring on nanocbor_put_bstr states that the return value is the number of bytes written.

NanoCBOR/include/nanocbor/nanocbor.h

Line 608 in 97e8cbe

 int nanocbor_put_bstr(nanocbor_encoder_t *enc, const uint8_t *str, size_t len); 

If you look at the source code the return value depends on the call to _fits which either returns 0 or -1. The docstring should probably be updated to something like:

• @return NANOCBOR_OK on success
• @return negative on error