Add rule for https://cdn.thinkific.com/ PDF reader.

[athyfr]

Thinkific uses its own PDF reader by default. This is completely unnecessary, as it is almost identical to Firefox's PDF reader (seems suspicious), and it is likely used for tracking:

https://cdn.thinkific.com/assets/pdf.js/2.7.570/web/viewer.html?file={Percent encoded PDF URL}

Please add a rule to ClearURLs for stripping this.