feature: edu resource subjects accordion filter group

[stephiescastle]

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Description

Addresses:

• https://github.com/nasa-jpl/www/issues/466

In cojunction with (many of these changes required updating www/apps/frontend/components/FetchListingIndex.vue):

• https://github.com/nasa-jpl/www/pull/551

Adds nested filter accordions by:

• Creating dynamic slots based on subFilter keys
• Populating dynamic slots in www/FetchListingIndex.vue to allow for reusing SearchFilterGroups and functionality already built to sync the url params with checkboxes
• Adding SearchFilterGroupAccordionItem component as a child component of SearchFilterGroups
• Checks route for subfilters and will automatically expand the appropriate accordion item if a sub-filter is in use.
• a bit verbose, code could probably be optimized, but this works for MVP

Instructions to test

Tested in the following environments/browsers:

Operating System

• macOS
• iOS
• iPadOS
• Windows

Browser

• Chrome
• Firefox ESR
• Firefox
• Safari
• Edge