fix indent not expanded in file comments

[HO-COOH]

Fix/Feature/Other

Fix

• Link to issue. If there is no issue please describe it using at least the issue template
  Closes File author template doesn't implement alignment option #206

Feature

• Added unit test

Also the @code command needs {.cpp} instead of .cpp as the language id block, see here, my bad!

[codecov]

Codecov Report

Merging #236 (b61400c) into master (638cfe0) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #236   +/-   ##
=======================================
  Coverage   93.36%   93.36%           
=======================================
  Files           5        5           
  Lines         814      814           
  Branches      242      242           
=======================================
  Hits          760      760           
  Misses         54       54           

Impacted Files	Coverage Δ
src/Lang/Cpp/CppDocGen.ts	99.60% <100.00%> (ø)

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[cschlosser]

Thank you!