Updated links from Slack to Discord

CONTRIBUTING.md

@@ -2,11 +2,11 @@
 
 Our software is open source so you can solve your own problems without needing help from others. And if you solve a problem and are so kind, you can upstream it for the rest of the world to use.
 
-Most open source development activity is coordinated through our [slack](https://slack.comma.ai). A lot of documentation is available on our [medium](https://medium.com/@comma_ai/)
+Most open source development activity is coordinated through our [Discord](https://discord.comma.ai). A lot of documentation is available on our [medium](https://medium.com/@comma_ai/)
 
 ## Getting Started
 
- * Join our slack [slack.comma.ai](https://slack.comma.ai)
+ * Join our [Discord](https://discord.comma.ai)
  * Make sure you have a [GitHub account](https://github.com/signup/free)
  * Fork [our repositories](https://github.com/commaai) on GitHub
 

README.md

@@ -31,7 +31,7 @@ openpilot is developed by [comma.ai](https://comma.ai/) and users like you.
 
 We have a [Twitter you should follow](https://twitter.com/comma_ai).
 
-Also, we have a several thousand people community on [slack](https://slack.comma.ai).
+Also, we have a several thousand people community on [Discord](https://discord.comma.ai).
 
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