docs: update readme links (#201)

We currently don't have a standardized contributing.md file.  Issue
templates handle most of "how to report a bug" and CI handles the rest.

README.md

@@ -101,7 +101,7 @@ cacache.get.byDigest(cachePath, integrityHash).then(data => {
 
 ### Contributing
 
-The cacache team enthusiastically welcomes contributions and project participation! There's a bunch of things you can do if you want to contribute! The [Contributor Guide](CONTRIBUTING.md) has all the information you need for everything from reporting bugs to contributing entire new features. Please don't hesitate to jump in if you'd like to, or even ask us questions if something isn't clear.
+The cacache team enthusiastically welcomes contributions and project participation! There's a bunch of things you can do if you want to contribute! Please don't hesitate to jump in if you'd like to, or even ask us questions if something isn't clear.
 
 All participants and maintainers in this project are expected to follow [Code of Conduct](CODE_OF_CONDUCT.md), and just generally be excellent to each other.