feat: add flag to export public keys

[aeneasr]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (1a40833) 76.03% compared to head (feac73a) 75.96%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
jwk/helper.go	50.00%	4 Missing and 4 partials ⚠️
cmd/cmd_create_jwks.go	60.00%	1 Missing and 1 partial ⚠️
cmd/cmd_get_jwks.go	83.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3684      +/-   ##
==========================================
- Coverage   76.03%   75.96%   -0.08%     
==========================================
  Files         134      134              
  Lines       10036    10065      +29     
==========================================
+ Hits         7631     7646      +15     
- Misses       1898     1906       +8     
- Partials      507      513       +6     

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