Use childNodes[2] for finding file resolution

ExLinks support vanilla 4chan and can add in its reverse image search link to the .fileText before 4chan X manages to parse it. As a result, 4chan X ends up looking at the reverse image search link for dimensions instead of the correct text element. Using childNodes[2] instead of lastChild fixes this.
Build pathnames taking into account the thread slug.
Merge pull request #1603 from Hupotronic/parsefile-fix

Use childNodes[2] for finding file resolution
Don't hide hr.desktop in threads.
Don't mess with the wrong <hr>.
Changelog.
Release 4chan X v3.20.11.
Rewrite the Filter.
Add per-filter anonymizing.
Close #854.
Recursive setting for filters.
Close #623.
Close #779.
Fix importing and conversion of old filters.
Re-arrange filter items to save some space.
Add importing/exporting of filters.
Close #942.
Focus the filter input when creating new filters.
Fix conversion of highlight class and pinning.
Move filter buttons at the top.
Create new filters at the top of the list.
Enable the save button immediately on text input.
Save the filter when pressing enter.
Filter exceptions. Close #792.
Filter notifications.