Simplify the architecture diagram

I like the "architecture" diagram of hvPlot shown at the top of the home page


But I think it could be simplified and cleaned up to community more clearly and be more easy to "speak to".

- change the 3 plotting arrows to one
- Align the arrows on the same horizontal line
- Align Holoviews and Datashader on the same vertical line
- Put the plotting backends into a dotted circle like the data libraries or remove the circles.
- Align to text headers on the same vertical line and consider if the number of characters could be meaningfully reduced.
- Consider if in any way there is room for indicating the `.interactive()` api as well.
- Add Streamz to the data sources
- Consider changing Dask, Geopandas, Pandas order to Pandas, Dask, GeoPandas to see the most well known data sources first.

The below quickly indicates the changes


or