Create a CSVTable Template

[jrg94]

I've been thinking about ways to extend the features of snakemd, and I think the direction the project should move is toward stabilizing the elements and not changing them. From there, templates can be made to extend the functionality that already exists. One way this would work really nicely is with the existing table feature. We can leave it as-is but provide a template that allows users to load a CSV into a table, so they don't have to do that by hand. Similar templates could be provided for tools like pandas, but that would need to be an external template.