Get facets showing again

Notes:

• It seems we, um, weren’t importing blacklight’s styles before (though maybe some were indirectly imported by blacklight maps or blacklight advanced search 🤷), so you might see some other things move around now that those styles are there.
• Where in CRDL we can just @import "blacklight"; in our SCSS to import blacklight and bootstrap, in DLG we need to @import "bootstrap"; @import "blacklight/blacklight"; Presumably it’s different because CRDL uses the blacklight-frontend npm package and DLG doesn’t. Not necessarily an issue, but something we might want to change so the code can be more similar between the two
• Blacklight’s responsive styles used to have three different layouts for the index page depending on window width. Going from large to medium made the facets get a little wider (in percentage terms), and at small screen sizes they collapsed. Now they just collapse at medium sizes; the middle step is gone. But we could bring it back if we want to.
• Much about the facet styles (e.g., background color) still needs to be changed