Possibly work around need to add final slash to root URLs when checking a link clicked by user

[Jaifroid]

For context see openzim/warc2zim#210 (comment). We currently handle the case of removing a final slash, but depending on the outcome of that issue, we might also need to handle the opposite case.

Note that if this ends up being handled at warc2zim2 level, we might be able to remove the current workaround.

EDIT: This is for zimit2, but the code is currently generalized and is also used for zimit1.