Add comparative colouring algorithm along with rudimentary initial write up

[mmcleod89]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 74.00000% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.13%. Comparing base (cc69f24) to head (af96135).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...c/IsomorphismChecker_python_serial/isomorphisms.py	79.11%	33 Missing ⚠️
src/IsomorphismChecker_python_serial/util.py	21.73%	18 Missing ⚠️
src/IsomorphismChecker_python_serial/colouring.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #69      +/-   ##
==========================================
- Coverage   94.77%   91.13%   -3.64%     
==========================================
  Files           9       10       +1     
  Lines         727      914     +187     
==========================================
+ Hits          689      833     +144     
- Misses         38       81      +43     

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