Add .Post-body class selector and exclude .no-fancybox class

[zxy19]

Add .Post-body class to image selector to avoid breaking other extension that adds images out of the post.
Add exclude class .no-fancybox to allow developer make their extension compatible with this one.

I found that this extension is breaking my extension user-decoration which will insert other img element without .Avatar class to user's avatar element. And These element were mistakely warped by fancybox.

I suppose that there's no need to select image in the whole .PostStream-item but only the .Post-body element which contains all the content of the post.

By the way, it's not so easy for developer to fix the compability with this extension so I add :not(.no-fancybox) so that developers can easily avoid their element to be warped.

[height]

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[iamdarkle]

Sorry I missed the notification. Thanks, appreciate the effort! Tagged under v1.1.4