Frontend 2.0

[HeinrichAD]

I documented the new features and created quite a few gifs. You can find them here. I find the PlantUML Language Features particularly nice.

IMPORTANT: Since this is a pretty big change and it is practically a re-implementation of the frontend, it would be appropriate if somebody else than myself could test the changes at least once before merging. I could bet that a few more bugs exist. Especially since I am no frontend export and also have no way to test browsers like Safari or Internet Explorer as well.

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Features:

• auto refresh function -- close #44
• light and dark theme
• monaco editor (vscode) with "apex" as syntax highlighting language
  • apex seems to work quite fine (better than no highlighting)
  • future possibility: own plantuml language syntax support
  • future possibility: autocomplete (to much work but maybe partial)
  • implemented example for !theme ...
  • implemented example for <&icon>
  • future possibility: code validation
  • implemented example for @start... and @end...:
    • should be the first or last command
    • should be of the some type (e.g. @startyaml and @endyaml)
    • should be used exactly once per document/diagram
• editor and preview is splitable into two windows like the "Extract window" functionality on plantuml.com
• multi index / multi paging diagram support -- close #7
• diagram can be displayed/rended as PNG, SVG, ASCII Art or PDF -- close #216
• Ctrl+s download the PlantUML Code as code file (diagram.puml)
• Ctrl+, opens the settings and Esc closes the settings

[arnaudroques]

Let's see what people say about it :-)

[HeinrichAD]

Puh. Risky. Let's see if you will revert the PR this time 😅. And let's hope that the feedback is not to catastrophic.