This commit documents the get-streams endpoint, which can be
by making a GET request to /api/v1/streams.
Note that in the code examples, JavaScript is missing an example
for how to pass in the `include_` query parameters. That is
because zulip-js's client.streams.retrieve function doesn't take
any arguments and zulip-js does not export any function equivalent
to client.call_endpoint in python-zulip-api/zulip.
This commit does the following:
* Move the Arguments table data from stream-message.md and
private-message.md to a JSON file.
* Add a Markdown extension that allows one to include and render
a table from a JSON file like so:
{generate_arguments_table|arguments.json|private-stream.md}
* Use Bootstrap's .table class to format the table instead of
relying on custom CSS.