Remove code duplication in shinyfeedback.js

[jcheng5]

Introduced a baseInputFeedback object that serves as a base class
for the other xxxInputFeedback implementations. Each impl need only
provide the methods that differ from the base class.

With these changes, I think the Shiny "feedback" custom message
handler can be slightly simplified--it should no longer be necessary
to hide() then show() for cases where feedback is shown twice in a
row for an input.

[jcheng5]

Note: The diff is a bit hard to make sense of at first, you might want to review the new version of the file first.

https://github.com/jcheng5/shinyFeedback/blob/dedupe-javascript/inst/assets/js/shinyfeedback.js

I tested these changes by running the supported_inputs_app example through shinytest, with and without valid values in all the inputs, and confirmed that the results are pixel-perfect.

[merlinoa]

Thanks @jcheng5 !! Yes this definitely reduces the code duplication and makes the input feedbacks more like shiny input binding with the base class and the $.extend() logic. Awesome!

One question on your comment:

With these changes, I think the Shiny "feedback" custom message
handler can be slightly simplified--it should no longer be necessary
to hide() then show() for cases where feedback is shown twice in a
row for an input.

Just to confirm, are you suggesting replacing this if/else block https://github.com/jcheng5/shinyFeedback/blob/3c1b7b2ad269e6920791a5ff0c900ca6552f0554/inst/assets/js/shinyfeedback.js#L444 with just feedbackFun.show(theInput, message)?

If so, yes I agree that this will be an improvement in both simplicity and functionality. I can make this change after merging this PR. Going to go ahead and merge now. Thanks!

[jcheng5]

Just to confirm, are you suggesting replacing this if/else block...

Yes, exactly. I haven't tested with that change but it sure seems like it should work.