Fix links in CONTRIBUTING.md (bytecodealliance#565)

Author: danbev

CONTRIBUTING.md

@@ -6,8 +6,8 @@ Wasmtime follows the same development style as Cranelift, so check out
 [Cranelift's CONTRIBUTING.md]. Of course, for Wasmtime-specific issues, please
 use the [Wasmtime issue tracker].
 
-[Bytecode Alliance] : https://bytecodealliance.org/
-[Code of Conduct] : CODE_OF_CONDUCT.md
-[Organizational Code of Conduct] : ORG_CODE_OF_CONDUCT.md
+[Bytecode Alliance]: https://bytecodealliance.org/
+[Code of Conduct]: CODE_OF_CONDUCT.md
+[Organizational Code of Conduct]: ORG_CODE_OF_CONDUCT.md
 [Cranelift's CONTRIBUTING.md]: https://github.com/bytecodealliance/cranelift/blob/master/CONTRIBUTING.md
 [Wasmtime issue tracker]: https://github.com/bytecodealliance/wasmtime/issues/new