Server render the table of contents in a collapsed state when the total
number of headings is equal or greater than the value of
`$wgVectorTableOfContentsCollapseAtCount`. Otherwise, the table of
contents will be server rendered in its "expanded" state.
In addition:
* Revise table of contents tests to call one `assertion` per element so
that it is easier to see the exact element that may fail an assertion.
* Revise table of contents tests to call a mount function that can merge
props to allow for a more flexible set of tests.
* Revise table of contents tests by wrapping a `describe` around tests
that expect the same prop state.
* Adds typedef for table of sections props
Bug: T300973
Depends-On: Ifaee451e1903f2accd0ada2f2ed6dfa3f83037b6
Change-Id: I382200bc603b6abf757a91f14a8a55a6581969bd
Collapses sub-sections in the new table of contents by default
(except for non-js and reduced-motion users) and expands the
sections when the top-level section link has been clicked.
Refactors the `activateSection` TableOfContents methods into separate
`activateSection` and `deactivateSection` functions.
Adds `expandSection` and `collapseSection` methods.
Adds triangle icon as a visual expand/collapsed indicator
next to all ToC section headings and are hidden via CSS based on
whether or not the section contains subsections.
Adds test for tableOfContents.
Bug: T299361
Change-Id: I36b3ae7f9f633877683bc17a9444c970d7fa7293
