feat: add support for InDel in FastaRecord

[not-a-feature]

This PR adresses #84 by introducing support for InDels.
The implementation aims to replicate the behavior of bcftools consensus.

Currently, the feature is enabled by default. To ensure backward compatibility, we could introduce a flag (defaulting to false) that allows users to omit InDels if needed.

I didn't have the time to perform some performance evaluation.
Feel free to keep open for further testing and validation.

[codecov]

Codecov Report

❌ Patch coverage is 73.91304% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.69%. Comparing base (0f97b76) to head (9705175).

Files with missing lines	Patch %	Lines
pyfaidx/__init__.py	73.91%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #240      +/-   ##
==========================================
- Coverage   88.81%   88.69%   -0.13%     
==========================================
  Files           2        2              
  Lines        1118     1132      +14     
==========================================
+ Hits          993     1004      +11     
- Misses        125      128       +3     

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[mdshw5]

Thanks for taking the time to implement this @not-a-feature. It's not a simple feature, and I want to take a bit of time to understand what you've done here before merging, but at first glance I really appreciate what you've done here. I also notice that bcftools consensus has a giant test suite that likely has some good tests if the goal is to implement similar behavior.