Microviewer

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* fix: paint uint64 arrays
* fix: select segments on uint64 arrays

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* fix: brushes are circular on rectangular images
* fix: use pixelated image rendering in chrome

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* perf: faster color assignment and rendering

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* feat: adds invert selection
* docs: numpy format link
* docs: add feature highlights
* docs: update demo image

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* fix: undo/redo seemingly working now
* feat: add date to file names
* feat: adjust canvas dimensions on axis rotation
* feat: add controls info about ctrl+z and ctrl+shift+z (undo/redo)
* feat: not perfect, but partly working undo/redo function
* feat: add segment selection to undo
* feat: add undo for painting
* fix: insertSquare can handle more data types

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* refactor: make HyperVolume a child class of SegmentationVolume
* fix: painting was broken for rectangular images
* fix: automatically select a new port if 8080 in use