Workaround for over-encoded URLs in zimit2

[Jaifroid]

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The first commit is a workaround for over-encoded URLs in zimit2.

However, we could also usefully check to see that we are handling clicks on URLs in Wikipedia articles where an encoded question mark that is not a querystring needs to be decoded. For example, an HTML URL like What_About_Me%3F_(Kenny_Rogers_album) needs to be decoded to A/What_About_Me?_(Kenny_Rogers_album) in order to find it in the ZIM and the material after the ? must not be removed.

Should fix #1229. Should only be merged pending the outcome of https://github.com/openzim/libzim/issues/865.