[lib] Support pending threads in URLInfo calculation

Summary:
Introduce support for calculating URL info for pending threads, as currently it could only parse URLs containing thread/<numbers>.
Because pending threads can have different forms of IDs, I added regular expression that recongnizes pending threads and correctly identifies pending ID returning it in URLInfo.

Test Plan:
Tested manually by refreshing page in different pending threads (after introducing modifications in next diffs, it doesn't work now because of no mechanism for pending threads creation in nav reducer as for now).
Tested automatically with different examples using: https://regexr.com/6q7os

Reviewers: tomek, atul, ashoat, abosh

Reviewed By: tomek, atul, abosh

Subscribers: ashoat, adrian, abosh

Differential Revision: https://phab.comm.dev/D4443