feat(#319): add optional change_type_order

[KyleKing]

Description

Implements proposed feature in #319. The default change type order is ["BREAKING CHANGE", "feat", "fix", "refactor", "perf"] (in descending order of importance) followed by any other change types in alphabetical order. In the configuration file, a user can override this setting to specify their own order and cover custom change types of interest.

Checklist

• Add test cases to all the changes you introduce
• Run ./script/format and ./script/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

The CHANGELOG should be ordered in the user-specified order rather than FIFO

Steps to Test This Pull Request

Run the standard pytest suite and see the two new test cases

Additional context

Fixes #319

Example use: KyleKing/calcipy@4a480a8

[codecov]

Codecov Report

Merging #323 (0e3482a) into master (aa2959d) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #323      +/-   ##
==========================================
+ Coverage   97.17%   97.20%   +0.02%     
==========================================
  Files          35       35              
  Lines         991     1000       +9     
==========================================
+ Hits          963      972       +9     
  Misses         28       28              

Flag	Coverage Δ
unittests	97.20% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/commands/changelog.py	97.40% <100.00%> (+0.10%)	⬆️
commitizen/cz/base.py	100.00% <100.00%> (ø)
commitizen/cz/customize/customize.py	94.11% <100.00%> (+0.50%)	⬆️
commitizen/defaults.py	100.00% <100.00%> (ø)

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[KyleKing]

I think this is all done. I cleaned up the commit history so that the first commit is just a refactor to move the commit tree to a global variable for use by my new tests. The diff on the second commit are the actual changes: e855269

I've tested the changes in my personal project and all seems to work well even with custom change types: KyleKing/calcipy@4a480a8

[woile]

Hi KyleKing, awesome work here! Minor correction, this is a new feature, so I'd like to ask you to rebase your PR using feat instead of fix, or if you want I can squash it and rename it, no problem.

[KyleKing]

@woile, thanks! Good point 🤦 I amended the commit message

[KyleKing]

I restored the white space changes and I think I addressed all of the comments. Thanks for the feedback!

[Lee-W]

@KyleKing Thanks for your rapid update! There's only one minor exception improvement I'd like to have. I think we're almost ready to merge this one! 🎉

[Lee-W]

@KyleKing Thanks for the latest update! Let's merge it back to master