The current helpers assume that a valid URL is a full URL (i.e. contains
the "://" separator between the scheme and domain). This isn't true, as
"file:" alone is parsed as a valid URL.
We must also avoid simply searching for the parsed public suffix in the
original URL string. For example, "com" is a public suffix. If we search
for that in the URL "com.com", we will think the public suffix starts at
index 0.
This is meant to serve as the method all Ladybird chromes can use to
highlight the eTLD+1 substring of the URL. It uses the Public Suffix
List to break the URL into 3 parts: the scheme and subdomain, the
eTLD+1, and all remaining parts (port, path, query, etc.).
After d2c7e1ea7d, there is now only one
user of LibPublicSuffix - the URL sanitation utility within LibWebView.
Rather than having an entire library for the small Public Suffix data
accessor, merge it into LibWebView.
We currently implement several forms of this method across the Ladybird
chromes. As such, we see commits to add special URL handling that only
affects a single chrome. Instead, let's consolidate all special handling
in a single location for all chromes to make use of.
This method can handle resolving file:// URLs, falling back to a search
engine query, and validation against the Public Suffix List. These cases
were gathered from the various chromes.
