Limit to footnote link itself

[RakoGames]

Specified only the link of the footnote itself; so the selector doesn't apply on other a elements in the footnote like collapsibles

Also the :is(.footnotes-footer, .bibitems) tag specifies the child a[href*=javascript] which is not beneficial to bibitems since wikidot doesn't add a link to these anyways and are only added to footnotes (unless a user add one inside the contents of one, in which case we do not want to target nor affect); so I changed it to specify the child .footnote-footer > a[href*=javascript] hence only affecting the footnotes only

should not cause any issues with my testing

[SYwaves]

While this does exclude collapsible links from being affected, this does not completely limit the range of a from being targeted in footnote-footer, and would still be affected by this bug: #245

A more comprehensive selector (that also won't raise specificity) would be something like:
& :where(.footnote-footer) > a:first-child::before
or
& :where(.footnote-footer) > a[onclick*="footnoteref"]::before