Farside now supports redirecting based on a provided link to a "parent"
service, if such a parent service is supported.
For example, a link such as:
farside.link/https://www.youtube.com/watch?v=dQw4w9WgXcQ
will now redirect to any of the available YouTube related frontends.
This works by matching against a mapping of "parent" service domains
("youtube.com", "reddit.com", etc) to a list of their respective frontend
alternatives (["invidious", "piped"], ["libreddit", "teddit"], etc). A
random element is chosen from this list, and the remainder of Farside's
routing logic proceeds as if the user had chosen the service directly to
begin with.
Closes#37
5006b97dfa