Set proper soversion.

[Vedingrot]

Soversion should only reflects the major version, since the soname
link cannot be created due to equal name as the library. Library
libQMaplibre.so.3.0.0 prevents soname libQMaplibre.so.3.0.0 from being
created.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.27%. Comparing base (80350b0) to head (26a4654).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #117   +/-   ##
=======================================
  Coverage   45.27%   45.27%           
=======================================
  Files          35       35           
  Lines        2125     2125           
=======================================
  Hits          962      962           
  Misses       1163     1163           

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[ntadej]

Thanks!