[ReadMe] Add Compliance Language

Add language parallel to what is in the OCI Runtime.

Signed-off-by: Rob Dolin <robdolin@microsoft.com>
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

README.md

@@ -27,6 +27,9 @@ The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SH
 
 The keywords "unspecified", "undefined", and "implementation-defined" are to be interpreted as described in the [rationale for the C99 standard][c99-unspecified].
 
+An implementation is not compliant if it fails to satisfy one or more of the MUST, REQUIRED, or SHALL requirements for the protocols it implements.
+An implementation is compliant if it satisfies all the MUST, REQUIRED, and SHALL requirements for the protocols it implements.
+
 ![](img/build-diagram.png)
 
 Once built the OCI Image can then be discovered by name, downloaded, verified by hash, trusted through a signature, and unpacked into an [OCI Runtime Bundle](https://github.com/opencontainers/runtime-spec/blob/master/bundle.md).