Create check_column_valid() to validate column class if needed.

[olivroy]

Summary

• SImplify input checking (test for option before column class as it should be quicker)
• Add some check_*() function usage
• Add some call argument to validate_currency() and validate_locale() for precise user message location
• Transform some help links into run links to be able to quickly visualize the info_*() reference table.

Not sure I understand the End support for gt_column() comment? I moved it around in some places, but not others

Checklist

• I understand and agree to the Code of Conduct.
• I have listed any major changes in the NEWS.
• I have added testthat unit tests to tests/testthat for any new functionality.

[rich-iannone]

the End support for gt_column() comment?

This is just to mark the end of the statements that dealt with running a formatter with different parameter values. And, this is actually an earlier name for the from_column() function (so it's now a typo). This set of comments could either be entirely removed (i.e., served its purpose during earlier development) or corrected.

[olivroy]

Ok, once you are done reviewing the PR, I will address your comments, and delete this comment

[rich-iannone]

LGTM, thank you!

[olivroy]

Ended up leaving the comment (and correcting), as it helps to make the code base clear!

Pushed some minor changes as well too.

[rich-iannone]

This is great, thanks again! Will merge now.