Only render display for a certain requested range of cells (perhaps with some overscan if needed)

[chrispsn]

trafficstars

That way we minimise what needs to be rendered to HTML (a big source of delay right now), and also what needs to be cloned across from the web worker.

The 'render' process will need to estimate the number of grid squares visible and request visual info for that many cells... (maybe needs to be smart with anything above it that has an arbitrary number of cells, requesting its length and then getting the right number of cells and just rendering that subset of values)

[chrispsn]

Useful? https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API