Export chart with Malloy CLI

[Ben8t]

Malloy charting capabilities are very nice and while it's possible to export then as PNG through VS Code, it's not possible to do the same via the CLI.

Use cases are many:

• being able to do a full T of ETL with Malloy as the main modelling semantic and being able to export corresponding chart for each model/views. I can see important workflow made in Python or R nowadays streamlines withon only Malloy modelling and new exporting capabilities
• create a self-serve chart/BI with Malloy CLI serving as backend for chart creation
• just export charts programatically

Interface Ideas:

malloy run <malloy_file> --export-charts=<true|false> --export-charts-format=<PNG|JPG|SVG|...>