Make plotly colorbar size scale with plot size

[stevenaleung]

Closes #4547

These changes improve the default positioning of the colorbars

using Plots
data = rand(3, 3);
heatmap(data)

and also allow the colorbar size to scale with plot size

heatmap(data, colorbar=:right, tickfont=30, xlabel="test")

[t-bltg]

Thanks for this PR, please read and use https://docs.juliaplots.org/stable/contributing/#Write-code,-and-format for the format check to pass.

I don't know anything about plotly, so someone else might want to review this.

[codecov]

Codecov Report

Base: 90.89% // Head: 90.95% // Increases project coverage by +0.05% 🎉

Coverage data is based on head (64f8fa2) compared to base (816d0f4).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4569      +/-   ##
==========================================
+ Coverage   90.89%   90.95%   +0.05%     
==========================================
  Files          40       40              
  Lines        7707     7802      +95     
==========================================
+ Hits         7005     7096      +91     
- Misses        702      706       +4     

Impacted Files	Coverage Δ
src/backends/gaston.jl	95.52% <0.00%> (-0.52%)	⬇️
src/backends/gr.jl	91.65% <0.00%> (-0.02%)	⬇️
src/args.jl	84.70% <0.00%> (ø)
src/animation.jl	99.04% <0.00%> (ø)
src/axes.jl	90.61% <0.00%> (+0.08%)	⬆️
src/utils.jl	92.61% <0.00%> (+0.08%)	⬆️
src/examples.jl	97.59% <0.00%> (+0.33%)	⬆️
RecipesPipeline/src/type_recipe.jl	94.44% <0.00%> (+5.55%)	⬆️

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[t-bltg]

Thanks !