Data Module: Improve Selectors/Actions docs

[youknowriad]

Related #7264

Now, that we generate markdown docs for Selectors and Actions, we need to make sure the wording used there is accurate and not redundant.

For instance: Actions shouldn't state that they return action objects.

Instead of Returns an action object used in signalling that block types have been added., write Signal that a block type, or types, have been added.

More details here #7264 (review)

[aduth]

Hmm, but they're worded as such because the functions alone do not signal anything, they do return action objects, even if in the typical sense they are only used in dispatching to a Redux store.

[tofumatt]

Yeah, but wording them all to say they just return an object doesn't imply how/why they're actually used. As mentioned in this comment, I think the middle ground is to say the entire set of functions returns the object, but then describe each function on the action it creates when passed to the store's dispatch() function.

Describing the actions all as just "functions that return objects" isn't very informative 😄

[youknowriad]

Seems like there's no consensus here, I'm closing this issue right now but we can still reconsider.