feat: provide the options to set arbitrary json encoder and decoder options

[MatthewDolan]

Issue #: #514

Description of changes:

Before this change, the lambda API supported setting some of the json encoder options (SetEscapeHTML(...) & SetIndent(...)). I needed the ability to set the UseNumber() option on the decoder and I considered setting it in the same way (by creating a one-off option), but instead I ended up creating two new options that allow setting arbitrary fields on the encoder and decoder.

I think this is a better option because it's future-proof (if new options are added to the json library, this library won't also need to be changed to make this option available) and more backward compatible.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #513 (a9dc75a) into main (771b391) will increase coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #513      +/-   ##
==========================================
+ Coverage   72.63%   72.86%   +0.23%     
==========================================
  Files          26       26              
  Lines        1407     1419      +12     
==========================================
+ Hits         1022     1034      +12     
  Misses        314      314              
  Partials       71       71              

Files Changed	Coverage Δ
lambda/handler.go	95.85% <100.00%> (+0.27%)	⬆️

[MatthewDolan]

@bmoffatt, I would be curious to hear your feedback on this change. Thank you.