Fix enum sizes

[ancapdev]

Enums in C are int, which are 4 bytes. Using single bytes is valid for representation, but not when sharing memory across the Julia/C boundary. This seems to fix the iteration example in #145.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.64%. Comparing base (6e1e3f4) to head (b24e4c1).

Files with missing lines	Patch %	Lines
src/bson.jl	50.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #149   +/-   ##
=======================================
  Coverage   80.64%   80.64%           
=======================================
  Files          11       11           
  Lines        1648     1648           
=======================================
  Hits         1329     1329           
  Misses        319      319           

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[ancapdev]

To the maintainers, do you have a governance process for packages under this org? For example, is there a set of assigned maintainers to each package that can be contacted to push through changes? This particular bug is critical and needs patching for 1.12 usage. I've made a few patches myself to this package over the years and wouldn't mind being added to the maintainers list and help get changes merged in.