Update spec to include language on default verification relationships, guidance on the alg property

[decentralgabe]

Fix #119 #47

• updated spec up version
• added guidance on default verification relationships for the identity key
• added guidance on the alg property
• updated algs to current (e.g. EdDSA -> Ed25519)
• added default algs to the registry
• defined key type and alg for X25519
• updated test vectors

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.05%. Comparing base (1b994fe) to head (1c39167).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #148   +/-   ##
=======================================
  Coverage   54.05%   54.05%           
=======================================
  Files          29       29           
  Lines        2146     2146           
=======================================
  Hits         1160     1160           
  Misses        872      872           
  Partials      114      114           

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