* shard: update to crystal 0.31.0
Additionally, no longer use the Crystal "markdown" library which has
been removed from the Crystal stdlib in version 0.31.0.
See https://github.com/crystal-lang/crystal/pull/8115.
Also fix some deprecation warnings using the following commands:
find . \( -type d -name .git -prune \) -o -type f -exec sed -i 's/URI\.escape/URI\.encode_www_form/g' "{}" \;
find . \( -type d -name .git -prune \) -o -type f -exec sed -i 's/URI\.unescape/URI\.decode_www_form/g' "{}" \;
sed -i 's/while \%pull\.kind \!\= \:end_object/until \%pull\.kind\.end_object\?/g' src/invidious/helpers/patch_mapping.cr
* Add prefers-color-scheme support
This should fix <https://github.com/omarroth/invidious/issues/559>.
The cookie storage format has been changed from boolean
("true"/"false") to tri-state ("dark"/"light"/""), so that users
without a cookie set will get dark mode if they have enabled the dark
theme in their operating system. The code for handling the cookie
state, along with the user's operating system theme, has been factored
out into a new function `update_mode`, which is called both at window
load and at the "storage" event listener, because the "storage" event
listener is only trigerred when a change is made to the localStorage
from another tab/window (for more info - see
<https://stackoverflow.com/a/4679754>).
