PR for v.1.2.3

[hcpchris]

• BUGFIX: Fixed error when loading certain Highcharts (JS) scripts in Jupyter context.
• ENHANCEMENT: Increased the default timeout for Chart.download_chart() and related.

[codecov]

Codecov Report

Merging #65 (88a802b) into master (a149dbb) will increase coverage by 0.29%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #65      +/-   ##
==========================================
+ Coverage   90.01%   90.31%   +0.29%     
==========================================
  Files         206      206              
  Lines       27495    27495              
  Branches     1786     1786              
==========================================
+ Hits        24750    24831      +81     
+ Misses       2044     1974      -70     
+ Partials      701      690      -11     

Impacted Files	Coverage Δ
highcharts_core/chart.py	40.12% <ø> (+2.77%)	⬆️
highcharts_core/headless_export.py	73.24% <ø> (ø)
highcharts_core/constants.py	95.70% <100.00%> (ø)
highcharts_core/metaclasses.py	63.34% <100.00%> (+9.43%)	⬆️

... and 11 files with indirect coverage changes