Add license headers and bump version

[marvinfriede]

No description provided.

[codecov]

Codecov Report

Merging #21 (bd80810) into main (f26ec4d) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #21      +/-   ##
==========================================
+ Coverage   97.93%   97.96%   +0.03%     
==========================================
  Files          15       15              
  Lines         339      344       +5     
  Branches       43       43              
==========================================
+ Hits          332      337       +5     
  Misses          5        5              
  Partials        2        2              

Impacted Files	Coverage Δ
src/tad_dftd3/damping/__init__.py	100.00% <ø> (ø)
src/tad_dftd3/damping/atm.py	100.00% <ø> (ø)
src/tad_dftd3/damping/rational.py	100.00% <ø> (ø)
src/tad_dftd3/defaults.py	100.00% <ø> (ø)
src/tad_dftd3/__version__.py	100.00% <100.00%> (ø)

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