Add bool decoding to the fuzzy decoder extension

[thfix13]

According to the table here, "fuzzy mode" should be able to support decoding multiple JSON types into a Go bool. However, that's not currently the case.

This PR adds a fuzzy bool decoder to the fuzzy decoder extension, with behaviour in line with the table (modulo arrays and objects, which don't seem to be handled for other Go types at the moment, either — the code to handle these is included anyway, commented out for consistency with other types).

[codecov]

Codecov Report

Merging #466 into master will decrease coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #466      +/-   ##
==========================================
- Coverage   86.52%   86.25%   -0.28%     
==========================================
  Files          41       41              
  Lines        5100     5100              
==========================================
- Hits         4413     4399      -14     
- Misses        546      560      +14     
  Partials      141      141              

Impacted Files	Coverage Δ
reflect_struct_decoder.go	82.68% <0.00%> (-1.87%)	⬇️

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