docs: Fill out the top-level contributing page a little

docs/contributing.md

@@ -1,3 +1,31 @@
 # Contributing
 
-... more coming soon
+We're excited to work on Wasmtime together with you! This guide should help you
+get up and running with Wasmtime development. But first, make sure you've read
+the [Code of Conduct](./contributing-coc.html)!
+
+## Join Our Chat
+
+We chat about Wasmtime development on Gitter — [join
+us!](https://gitter.im/CraneStation/Lobby)
+
+If you're having trouble building Wasmtime, aren't sure why a test is failing,
+or have any other questions, feel free to ask here. You can also [open an
+issue](https://github.com/bytecodealliance/wasmtime/issues/new)!
+
+## Finding Something to Hack On
+
+If you're looking for something to do, these are great places to start:
+
+* [Issues labeled "good first
+  issue"](https://github.com/bytecodealliance/wasmtime/labels/good%20first%20issue)
+  — these issues tend to be simple, what needs to be done is well known,
+  and are good for new contributors to tackle. The goal is to learn Wasmtime's
+  development workflow and make sure that you can build and test Wasmtime.
+
+* [Issues labeled "help
+  wanted"](https://github.com/bytecodealliance/wasmtime/labels/help%20wanted)
+  — these are issues that we need a little help with!
+
+If you're unsure if an issue is a good fit for you or not, feel free to ask in a
+comment on the issue, or in chat.