Style/usability enhancements

[omgmog]

This is more for the sake of keeping track of some issues I've noticed, before I or others get a chance to resolve them.

• Footer not present across all pages (Fixed in Footer on all pages #18)
• Footer balancing (visual)
• Link hover/active/visited styles
• Text/background contrast
• target="_blank" on external links (and perhaps rel="nofollow" 🤷)
• Check cross-device/browser, the vmax/vmin/vh/vw units might not behave as expected everywhere...
• Remove even more of the boilerplate styles from the base template. AFAIK we're not using any of the .tdbc-* stuff now?
• The language around past/future events might be a bit clunky when the event is occurring Expanded below.
• The og:image twitter:image meta tags have incorrect values
• The /feed/ isn't populated

Feel free to add anything else and create a PR for any fixes 💯

[omgmog]

Regarding language around future/occurring/past events

Future:

• event has date, before the event this is in the future

Occurring:

• event has date, when the event is happening this is in the past

Past:

• event has date, this is in the past
• event has happened: true flag too

This would also need some changes to the occured filter (also that's a typo!) to cater to all 3 cases.