Click event on underlying hidden field should focus editor #1
Description
In GroupWorkspaceForm we have a visually-hidden label whose purpose appears to be screenreader accessibility; when clicked, it focuses the editor (using functionality provided by this package) and sets the cursor position (using custom prosemirror trickery).
However, the jsx-a11y eslint rules complain if you add click handlers to non-interactive elements, including label. This seems fair enough.
Ideally we'd apply this handler to the label's related input element, which also receives a click event if its associated label is clicked, and is an interactive element. In this case the related input element is a hidden input rendered by the markdown-editor tool.
It seems reasonable to build this functionality into markdown-editor; if the hidden field receives a click event, that means someone's clicked on an associated label, so we should focus the editor. This means clients can use the editor more like a regular input element and still have expectations met.
The editor does expose a focus() method (I believe this is provided by prosemirror?), however GroupWorkspaceForm doesn't purely use this; it also does some extra prosemirror magic to set the cursor to the start of the text box. Presumably that's perfectly doable here, too.
In summary: let's do that thing that I said.