[OpenID-Specs-eKYC-IDA] Issue #1340: Improve wording in attachments section (openid/ekyc-ida)

[Daniel Fett]

New issue 1340: Improve wording in attachments section
https://bitbucket.org/openid/ekyc-ida/issues/1340/improve-wording-in-attachments-section

Daniel Fett:

* Hashes should be taken over the document bytes \(not the HTTP payload that might be encoded in some way\)
* “Base64 encoded representation of the cryptographic hash.” → “Base64-encoded \[@RFC4648\] bytes of the cryptographic hash”

‌