Fixes #3383 ('Variables' sections on docs page)

[avt613]

This is a documentation fix.

Related to issue #3383

There are 2 Variables sections on the variables page with the same ID's and no gap between them. The right hand menu shows 2 Variable sections which both take you to the first one of the 2 variable sections.

Proposed solution

1. Give each variables section a different name, by using the anchor_name as the section title
2. Add gap between consecutive variable 'divs' (identified by class="bd-vars")

Tradeoffs

None that I can see.

Testing Done

Some...
Fixes problem on the variables page, but may cause unintended issues on other pages which use the modified file if they have an anchor_name set which should not be used for the section title.

Changelog updated?

No.

Screenshot

[avt613]

Thanks for merging.
The scss for the Bulma docs has not been recompiled yet.
Is this done automatically or does it need to be done manually? (The other change has already taken affect)