Add placeholders or skeletons to components

[archiewood]

Steps To Reproduce

1. Start a fresh Evidence project and wait for the browser to open
2. Observe the browser

Expected Behavior

There is some static image or placeholder of a chart visible when the page is loading

Actual Behaviour

Some components are not visible while the page loads.
This includes the Charts and the Query Viewer, but not the DataTable, Value or BigValue

[mcrascal]

I don't think this is a bug, we just don't have skeleton states in most (all) of the components, given how fast they are already. @ItsMeBrianD has done some work on this on next.

[archiewood]

I don't understand why the DataTable loads instantly in the initial HTML but the QueryViewer does not (for example)

[csjh]

I think that's because we default to not showing QueryViewer, so it isn't SSR'd

[mcrascal]

That's right -- you could set it to be included by default during SSR but then it would jank off the page for most folks who have queries hidden.

[mcrascal]

Queryviewer is a bit of a special case, but SSR'ing the charts would definitely be a good improvement

[csjh]

ECharts SSR'd charts are currently more of an embedded thing (i.e. something you would return from an endpoint and you link to it as a .png or such) but apache/echarts#18334 could be a very interesting feature to keep an eye on