Make commands clickable in help message

[JasonWeill]

Problem

Users can see which commands they can use in the chat UI on load or by running /help (see #93, #277), but they need to type or copy and paste the commands to run them.

Proposed Solution

In the chat help message, when a user clicks on a command, it is prepopulated in the chat box.

Additional context

Consider also providing templates for required and optional arguments in the chat box.