Update contributing link
:+1::tada: First off, thanks for taking the time to contribute! :tada::+1:
-You can read [How to Contribute](https://app.gitbook.com/@continualai/s/avalanche/how-to-contribute/guidelines) on the Official Avalanche Website.
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+You can read [How to Contribute](https://avalanche.continualai.org/how-to-contribute/guidelines) on the Official Avalanche Website.
