Add a lint rule to require at least some docs if jsdoc is defined

[turt2live]

The following is not helpful, for example:

/**
 * @param {string} roomId
 * @param {string} userId
 * @param {string} reason Optional.
 * @param {module:client.callback} callback Optional.
 * @return {Promise} Resolves: TODO
 * @return {module:http-api.MatrixError} Rejects: with an error response.
 */

This repeated a number of times through our code.

[richvdh]

The following is not helpful, for example:

Is this in react-sdk/element-web or js-sdk?

If the former, I don't think they attempt to publish jsdoc so I agree it's not helpful (but then I'd argue that the solution is not to require more jsdoc).

If js-sdk, then prior to matrix-org/matrix-js-sdk#2869, this was better than nothing, because it meant at least the types and param names made it into the jsdoc. That stuff is populated automatically now, so yes it's not helpful. Still, I'm not in a rush to rip it all out.

[turt2live]

This was in the js-sdk (contet clue being the module:http-api.MatrixError weirdness)