Update versions in pom.xml and documentation after 0.3.0 release

[github-actions]

• Versions are updated in pom.xml, README.md and in examples
• Current project version is incremented to the next snapshot

[codecov]

Codecov Report

Merging #690 (9ae4c96) into master (c4b6084) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #690   +/-   ##
=========================================
  Coverage     79.94%   79.94%           
  Complexity     1839     1839           
=========================================
  Files            87       87           
  Lines          4801     4801           
  Branches       1549     1549           
=========================================
  Hits           3838     3838           
  Misses          241      241           
  Partials        722      722           

Flag	Coverage Δ	Complexity Δ
unittests	79.94% <ø> (ø)	0.00 <ø> (ø)

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