Link to github for flytekit docs

[thomasjpfan]

Why are the changes needed?

With this PR, the flytekit API docs will point to Github.

What changes were proposed in this pull request?

This PR adds a custom linkcode_resolve to link back to flytekit code.

How was this patch tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.35%. Comparing base (da2ce74) to head (9ec2a5e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5831   +/-   ##
=======================================
  Coverage   36.34%   36.35%           
=======================================
  Files        1304     1304           
  Lines      110148   110148           
=======================================
+ Hits        40037    40042    +5     
+ Misses      65944    65939    -5     
  Partials     4167     4167           

Flag	Coverage Δ
unittests-datacatalog	51.37% <ø> (ø)
unittests-flyteadmin	55.60% <ø> (+0.03%)	⬆️
unittests-flytecopilot	12.17% <ø> (ø)
unittests-flytectl	62.21% <ø> (ø)
unittests-flyteidl	7.17% <ø> (ø)
unittests-flyteplugins	53.35% <ø> (ø)
unittests-flytepropeller	42.02% <ø> (ø)
unittests-flytestdlib	55.35% <ø> (-0.03%)	⬇️

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