docs: fix wrong link

If you want to join us, see https://doocs.github.io/#/?id=how-to-join for details.

Author: yanglbme

README.md

@@ -9,7 +9,7 @@
   <a href="https://github.com/doocs/leetcode/network/members"><img src="https://img.shields.io/github/forks/doocs/leetcode.svg" alt="forks"></a>
   <a href="https://github.com/doocs/leetcode/blob/master/LICENSE"><img src="https://badgen.net/github/license/doocs/leetcode?color=green" alt="LICENSE"></a><br>
   <a href="http://makeapullrequest.com"><img src="https://badgen.net/badge/PRs/welcome/cyan" alt="PRs Welcome"></a>
-  <a href="https://github.com/doocs/intro"><img src="https://badgen.net/badge/organization/join%20us/cyan" alt="open-source-organization"></a>
+  <a href="https://doocs.github.io/#/?id=how-to-join"><img src="https://badgen.net/badge/organization/join%20us/cyan" alt="open-source-organization"></a>
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   <a href="#sponsors" alt="Sponsors on Open Collective"><img src="https://opencollective.com/doocs-leetcode/sponsors/badge.svg" /></a> -->
 </p>