enh: added new PlotlyBase methods for SyncPlot

[sglyon]

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[codecov-commenter]

Codecov Report

Merging #414 (015884e) into master (0224ca7) will decrease coverage by 0.86%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #414      +/-   ##
==========================================
- Coverage   39.01%   38.14%   -0.87%     
==========================================
  Files           4        4              
  Lines         264      270       +6     
==========================================
  Hits          103      103              
- Misses        161      167       +6     

Flag	Coverage Δ
unittests	38.14% <0.00%> (-0.87%)	⬇️

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Impacted Files	Coverage Δ
src/PlotlyJS.jl	24.13% <0.00%> (-2.79%)	⬇️

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