Add README

Establish the motivation and purpose of this repository.

README.md

@@ -0,0 +1,19 @@
+# user-tools
+
+This repository contains community contributed tools. This is different from
+[official bpftrace tools][0] in that we do not intend to be as strict about
+requirements.
+
+Thus, we encourage users to contribute anything they find useful for the
+community. Motivations could include (but are not limited to):
+
+* Sharing useful functionality
+* Sharing novel techniques
+* Incubating a new official tool
+
+One intention is that all new official tools begin life in this repository. And
+over time we'll develop some criteria for promoting a user tool to an official
+tool that bpftrace maintainers will help support over long periods of time.
+
+
+[0]: https://github.com/bpftrace/bpftrace/blob/master/CONTRIBUTING-TOOLS.md