Add support for multiple signer

[dajiaji]

No description provided.

[codecov]

Codecov Report

Merging #35 (010f38a) into main (6b415e2) will increase coverage by 2.21%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   94.38%   96.59%   +2.21%     
==========================================
  Files          14       14              
  Lines         872      880       +8     
  Branches      203      206       +3     
==========================================
+ Hits          823      850      +27     
+ Misses         36       20      -16     
+ Partials       13       10       -3     

Impacted Files	Coverage Δ
cwt/cose.py	87.82% <100.00%> (+18.66%)	⬆️

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