Added keyring tip

[jesper-friis]

Description

Added small tips about how to use keyring with tripper.

Also added keyring as a requirement for datadoc.

Type of change

• Bug fix and code cleanup
• New feature
• Documentation update
• Testing

Checklist for the reviewer

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?
• Is the code properly tested?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.98%. Comparing base (5c0ca3f) to head (790c92e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #449   +/-   ##
=======================================
  Coverage   83.98%   83.98%           
=======================================
  Files          30       30           
  Lines        4140     4140           
=======================================
  Hits         3477     3477           
  Misses        663      663           

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