Ideally the TOC has an h2 after the article title h1, but because of the TOC sticky positioning and its placement in the grid, we cant use an h2 without messing up the heading order.
Bug: T301051
Change-Id: I462ddfb618ddd422c9f71293280d1790c4846f50
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
