update github link

Author: Ivan Leider

index.html

@@ -172,7 +172,7 @@
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                         <header>How can I contribute?</header>
-                        <section>Firecracker is an AWS open source project that encourages contributions from customers and the developer community. Any contribution is welcome as long as it aligns with our <a href="https://github.com/firecracker-microvm/firecracker/CHARTER.md">charter</a>. You can learn more about how to contribute in <a href="https://github.com/firecracker-microvm/firecracker/CONTRIBUTE.md">CONTRIBUTE.md</a>. You can chat with others in the community on the <a href="https://firecracker-microvm.slack.com">Firecracker Slack workspace</a>.</section>
+                        <section>Firecracker is an AWS open source project that encourages contributions from customers and the developer community. Any contribution is welcome as long as it aligns with our <a href="https://github.com/firecracker-microvm/firecracker/blob/master/CHARTER.md">charter</a>. You can learn more about how to contribute in <a href="https://github.com/firecracker-microvm/firecracker/blob/master/CONTRIBUTE.md">CONTRIBUTE.md</a>. You can chat with others in the community on the <a href="https://firecracker-microvm.slack.com">Firecracker Slack workspace</a>.</section>
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