Add option to inline chart data into a chart

[mpickering]

I would find it useful sometimes if it was possible to generate a standalone vega-lite specification which could be loaded into the vega editor to play around with different rendering options. It could also be useful for embedding eventlog2html visualisations into a blog post for example.

There could be options to generate each of the different chart types which would directly embed the data into the specification or write the data to a file and use that instead of the named data range.