Tell ImGui that changing mouse cursors is supported

[Auburn]

Allows ImGui setting ImGuiIO::ConfigWindowsResizeFromEdges to function

[codecov-commenter]

Codecov Report

Merging #71 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
+ Coverage   75.27%   75.30%   +0.02%     
==========================================
  Files          21       21              
  Lines         902      903       +1     
==========================================
+ Hits          679      680       +1     
  Misses        223      223              

Impacted Files	Coverage Δ
src/Magnum/ImGuiIntegration/Context.cpp	87.50% <100.00%> (+0.07%)	⬆️

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[mosra]

Oh, of course I forgot about this. Merged as 0808728, sorry for the delay.