## Summary
There is a new official URL for the typing documentation:
https://typing.python.org/
Change all https://typing.readthedocs.io/ links to use the new sub
domain, which is slightly shorter and looks more official.
## Test Plan
Tested to see if each and every new URL is accessible. I noticed that
some links go to https://typing.python.org/en/latest/source/stubs.html
which seems to be outdated, but that is a separate issue. The same page
shows up for the old URL.
## Summary
After I was asked twice within the same day, I thought it would be a
good idea to write some *user facing* documentation that explains our
reasoning behind inferring `Unknown | T_inferred` for public uses of
undeclared symbols. This is a major deviation from the behavior of other
type checkers and it seems like a good practice to defend our choice
like this.