Allow use of default field formatters, even with custom formatting string

[dgkf]

This PR changes some of the internal behaviors to hopefully make it easier to customize.

There is still a default format, but it is functionally much simpler. Instead, each of the fields get their own formatters, which are implemented as methods on as.character. This means that glue::glue() will automatically leverage these formatters when building the documentation.

This mean a format such as ({type})\cr {description} will automatically wrap naked types in backticks and respect quotes the same way the default formatter does.

If one prefers to work with the raw values, they can always use ({unclass(type)}) unclass(description) or provide the formatter as a function.

[codecov]

Codecov Report

Merging #13 (c349be0) into main (713d79d) will increase coverage by 2.94%.
The diff coverage is 78.94%.

❗ Current head c349be0 differs from pull request most recent head 47bb24f. Consider uploading reports for the commit 47bb24f to get more accurate results

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   83.00%   85.95%   +2.94%     
==========================================
  Files          11       11              
  Lines         353      363      +10     
==========================================
+ Hits          293      312      +19     
+ Misses         60       51       -9     

Impacted Files	Coverage Δ
R/tag_typedreturn.R	0.00% <0.00%> (ø)
R/tag_typed.R	71.42% <75.00%> (+12.60%)	⬆️
R/utils.R	91.66% <100.00%> (+21.29%)	⬆️

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