Support entering wildcard(s) in element picker's network filters

[gorhill]

In the element picker dialog box, a user may further edit the proposed network filter(s), and entering wildcard(s) as part of the filter should be supported since ABP filter syntax allows wildcards, useful for parts of a filter which are known to be variable.

Currently, if a user uses wildcard(s) in a proposed network filter in the element picker, the element picker will find no match on the page (nothing is highlighted), and as a result the element picker won't allow the filter to be created, even though wildcards are legitimate as per filter syntax.