Make clicking title in docs behave like toggle button

[kkemple]

This PR makes the behavior between clicking a title and the accompanying button the same.

Closes #7975

[fk]

Ah, closeSidebar! That of course made a lot more sense in the context of Gatsby v1. All the sidebar stuff started as #6076 against www on v1 (and mostly borrowing the reactjs.org sidebar implementation 🙏), where the sidebars were part of the layout, and never got removed from the DOM when switching location.

IMO closeSidebar does still make sense for Gatsby v2 www for mobile and the anchor links in the Tutorial (https://next.gatsbyjs.org/tutorial/part-zero/#overview-of-core-technologies) …having a hard time putting thoughts into words, long day…lemme record a video! 😄

OK, here's the one good thing closeSidebar is still doing and IMO is worth preserving:
https://www.dropbox.com/s/yj6dl1wx788vpwm/closeSidebar.mov?dl=0

[LekoArts]

@kkemple @fk What's the status here? 😊

[fk]

@LekoArts 🤗
Good question…"forgotten" is the status I guess! 😅

IIRC my comment explains that while this PR does fix the connected issue, it does so at the expense of closeSidebar. IMO we should keep closing the sidebar when clicking a link.

[LekoArts]

@fk So could we close this PR then? Or what's the plan?

[calcsam]

Let's close this as it's stale and merge conflicts.

@fk you can re-open if we want to do something like this later.