Also enable collapsing from the closing part of a section

[Mumeii]

Whenever I edit a .js file, I can only use the collapse buttons on the opening part of a section

... not its closing one :

Been able to do so would be a time saver, especially whenever I'm working on test files that embed big chunks of mocking objects.

By big chunks I mean several hundreds of lines 😋

[aeschli]

Duplicate of #60670