Change naming from incl_btw to incl_vat

[klaasnicolaas]

Proposed change

Adjusted to a correct English name for VAT, and from now on it is a bool and no longer a string value.

Additional information

• This PR fixes or closes issue: fixes #

Checklist

• I have updated the documentation if needed.
• I have updated the tests if needed.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (9168436) 100.00% compared to head (ebbb735) 100.00%.

❗ Current head ebbb735 differs from pull request most recent head e0d6e1f. Consider uploading reports for the commit e0d6e1f to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #219   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          160       160           
  Branches        18        18           
=========================================
  Hits           160       160           

Files	Coverage Δ
src/energyzero/energyzero.py	100.00% <100.00%> (ø)

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