Update to drawio 21.1.4

[bollwyvl]

Changes

• [x] update to drawio 21.0.2
• [x] update to draw-image-export2 1.0.2
• [x] bump minimum python to 3.8
• [x] remove lerna
• [x] update patches
• [x] update theme

[codecov[bot]]

Codecov Report

Merging #112 (b2df84a) into master (606fd70) will increase coverage by 0.57%. The diff coverage is 66.15%.

@@            Coverage Diff             @@
##           master     #112      +/-   ##
==========================================
+ Coverage   59.04%   59.61%   +0.57%     
==========================================
  Files          14       14              
  Lines         542      567      +25     
  Branches       76       80       +4     
==========================================
+ Hits          320      338      +18     
- Misses        220      225       +5     
- Partials        2        4       +2     

Impacted Files	Coverage Δ
.../ipydrawio-export/src/ipydrawio_export/_version.py	100.00% <ø> (ø)
...wio-export/src/ipydrawio_export/serverextension.py	100.00% <ø> (ø)
...pydrawio-mathjax/src/ipydrawio_mathjax/_version.py	100.00% <ø> (ø)
py_packages/ipydrawio/src/ipydrawio/__init__.py	83.33% <0.00%> (+11.90%)	:arrow_up:
py_packages/ipydrawio/src/ipydrawio/_version.py	100.00% <ø> (ø)
py_packages/ipydrawio/src/ipydrawio/app.py	0.00% <0.00%> (ø)
py_packages/ipydrawio/src/ipydrawio/clean.py	0.00% <ø> (ø)
...s/ipydrawio-export/src/ipydrawio_export/manager.py	60.88% <59.09%> (+0.11%)	:arrow_up:
.../ipydrawio-export/src/ipydrawio_export/__init__.py	100.00% <100.00%> (ø)
...kages/ipydrawio-export/src/ipydrawio_export/app.py	94.11% <100.00%> (+0.08%)	:arrow_up:
... and 4 more

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