Curve editor example app

[dlyr]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Add a piecewise cubic Bezier class and a new example app of a curve editor.

• What is the current behavior? (You can also link to an open issue here)
  Not existing.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  None.

• Other information:
  This PR is based on the PR Fix assets #966
  A getter of the brush radius had to be added to the renderer.

[codecov]

Codecov Report

Merging #967 (d3a2bbe) into release-candidate (4dcf7d0) will decrease coverage by 0.30%.
The diff coverage is 0.00%.

❗ Current head d3a2bbe differs from pull request most recent head e11bb2e. Consider uploading reports for the commit e11bb2e to get more accurate results

@@                  Coverage Diff                  @@
##           release-candidate     #967      +/-   ##
=====================================================
- Coverage              45.65%   45.36%   -0.30%     
=====================================================
  Files                    312      314       +2     
  Lines                  23060    23209     +149     
=====================================================
  Hits                   10529    10529              
- Misses                 12531    12680     +149     

Impacted Files	Coverage Δ
src/Core/Geometry/Curve2D.cpp	0.00% <0.00%> (ø)
src/Core/Geometry/Curve2D.hpp	0.00% <0.00%> (ø)
src/Engine/Rendering/Renderer.hpp	7.27% <0.00%> (-0.42%)	⬇️

... and 1 file with indirect coverage changes