Add support for transparent image in overlay module

[rishabhshuklax]

Fixes #1605

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[rishabhshuklax]

@publiclab/is-reviewers please review this

[codecov]

Codecov Report

Merging #1606 into main will decrease coverage by 1.21%.
The diff coverage is 47.61%.

@@            Coverage Diff             @@
##             main    #1606      +/-   ##
==========================================
- Coverage   66.67%   65.46%   -1.22%     
==========================================
  Files         130      133       +3     
  Lines        2686     2748      +62     
  Branches      433      440       +7     
==========================================
+ Hits         1791     1799       +8     
- Misses        895      949      +54     

Impacted Files	Coverage Δ
src/Modules.js	100.00% <ø> (ø)
src/modules/EdgeDetect/Module.js	100.00% <ø> (ø)
src/modules/WebglDistort/Module.js	2.29% <0.00%> (ø)
src/modules/ColorHalftone/Module.js	3.63% <3.63%> (ø)
src/modules/Overlay/Module.js	93.18% <94.11%> (-1.69%)	⬇️
src/modules/ColorHalftone/index.js	100.00% <100.00%> (ø)
src/modules/Colorbar/Module.js	100.00% <100.00%> (ø)
src/modules/Crop/Module.js	88.88% <100.00%> (ø)
src/modules/EdgeDetect/EdgeUtils.js	86.81% <100.00%> (-0.15%)	⬇️
src/modules/Resize/Module.js	100.00% <100.00%> (ø)
... and 4 more

[gitpod-io]

[harshkhandeparkar]

All hail ES6,7.8.9.10 and even soon to come 11!

[rishabhshuklax]

@jywarren could review this too!

[jywarren]

Thanks folks! Great to be moving again, thanks for all your help!!