Add file type: IBW

[SylviaWhittle]

Closes #17

This PR adds IBW support

Just basic loading of .ibw files, akin to how I did .spm.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 31 lines in your changes are missing coverage. Please review.

Project coverage is 67.62%. Comparing base (f282c31) to head (85ffb11).
Report is 74 commits behind head on main.

Files	Patch %	Lines
topofileformats/spm.py	63.15%	14 Missing ⚠️
topofileformats/jpk.py	80.43%	9 Missing ⚠️
topofileformats/ibw.py	78.94%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   65.87%   67.62%   +1.75%     
==========================================
  Files           3        6       +3     
  Lines         337      451     +114     
==========================================
+ Hits          222      305      +83     
- Misses        115      146      +31     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ns-rse]

Great work burning through these @SylviaWhittle

Some comments inline.

You'll likely encounter merge conflicts in the subsequent commits, in the README.md and possibly example_01.ipynb. They should be straight-forward to resolve though.

[ns-rse]

Can't understand why all the other changes have appeared on this branch, particularly as they are already on main.

One tiny suggestion for the disabled pylint to make it easier for readers to know what has been disabled otherwise ready to go.