contour plot speed improvement

Currently the coordinates are recalculate each time we zoom in / out or pan and using a benchmark this seems time consuming.

https://github.com/cheminfo/nmr-displayer/blob/5b5ac2b8a88f5793a49704daded2eca6a0b7dd9f/src/component/2d/Contours.jsx#L30-L41

When the domain changes could we not simply apply a translate and a scale.

https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/transform

We should take care to add this attribute so that the line with is not scaled: https://stackoverflow.com/questions/10357292/how-to-make-stroke-width-immune-to-the-current-transformation-matrix

@targos Does this make sense ?