Export BinaryOperator function

[kblomster]

This PR exports a BinaryOperator function that is similar in spirit to jet.Func, but for custom/unsupported operators rather than for functions. See #338

This is kind of a proof-of-concept PR; maybe this should have tests? It should probably have docs as well.

Maybe there should also be a UnaryOperator and a TernaryOperator but at least from my perspective I don't foresee a huge need for those.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 90.39%. Comparing base (1fd423b) to head (1d31062).

Files	Patch %	Lines
internal/jet/operators.go	0.00%	2 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #339      +/-   ##
==========================================
- Coverage   90.42%   90.39%   -0.03%     
==========================================
  Files         125      125              
  Lines        7434     7436       +2     
==========================================
  Hits         6722     6722              
- Misses        552      554       +2     
  Partials      160      160              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[go-jet]

LGTM. 👍