added simple install target to CMakeList

[DerThorsten]

Hi,
I would like to add this package to conda-forge.
It would simply things a lot to have an install target in the CMakeList to install the headers with
make install

Greetings DerThorsten

[codecov-commenter]

Codecov Report

Merging #7 (9798216) into master (5e88e23) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #7   +/-   ##
=======================================
  Coverage   89.68%   89.68%           
=======================================
  Files          20       20           
  Lines        1319     1319           
=======================================
  Hits         1183     1183           
  Misses        136      136           

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[matusnovak]

Hi @DerThorsten

Thank you for the contribution. I apologize for not being able to look at it sooner.