Auto expand instance method documentations

[PaulKinlan]

No clue why you are hiding it, you've links to the heads so the user can auto jump to the correct instance method documentation....

Background: I was cursing you all for not documenting https://workboxjs.org/reference-docs/latest/module-workbox-build.html#.getFileManifestEntries until I realised that if I clicked on it then I get the documentation... Would love it if you don't have to make people like me think about what to do.

[gauntface]

The thinking / rational was this it looks super bloated if you have everything opened up by default, but agree that it's not obvious if you are new to the site.

Will have a think on what we can do here.