down almost 100 lines of code!

(and hopefully denotationally equivalent, except for the bits about
where it was wrong before and didn't replace uris correctly)

(unfortunately this one's hardcoded, the config options just aren't
general enough)

(points behave slightly differntly than I thought)

obviously, it should remove all objects defining badges, not those NOT
defining badges …

(and `url` is, too)

(since we're starting to get maps that actually pass linting, we also
get to find more bugs! yay!)

these now have their own top-level config attribute which is essentially a
shorthand for setting one that's deeper nested.

(this seems to be a common mistake so far)

(before it would fail to find e.g. the start layer if it wasn't a
top-level layer)

The script inject doesn't do anything for now; guess I'll re-add that
once we actually have a URI for that.

(these were `error` before, which didn't really make sense, since
workadventure can deal with them, they're just not allowed at rc3)

also, float properties exist, apparently

(in which case it just doesn't do anything at all)

(the format used last year is no longer applicable to this year's event)

(found by running through rc3 2021 map submissions and looking at what failed)

(as per today's discussion with tabascoeye, mapCopyright should not be
required, though I've left it as recommended)

(previously it would just lint "can't use name twice" multiple times,
which looks kind of silly)