Flesh out blank how-to-contribute page

Author: schoen

docs/resources/contribute.md

@@ -1 +1,11 @@
-instructions on how to help the project
+## How to help the Simplicity project
+
+You can help Simplicity by participating in any of the [projects built with it](../../use-cases), or by building your own applications.
+
+To contribute to the Simplicity and SimplicityHL open source projects, please see
+
+* [Simplicity language project](https://github.com/BlockstreamResearch/simplicity/)
+* [Contributing to SimplicityHL](https://github.com/BlockstreamResearch/SimplicityHL/blob/master/CONTRIBUTING.md)
+* [Contributing to docs.simplicity-lang.org](https://github.com/BlockstreamResearch/simplicity-lang-org/blob/main/CONTRIBUTING.md) (this website)
+
+See [Blockstream Research's GitHub repositories](https://github.com/orgs/BlockstreamResearch/repositories) for more open source projects related to Simplicity and Blockstream Research's other work areas.