docs/runtime-compliance-testing: Document list of supported APIs

Currently just the command line API, but the test suite might add
support for more APIs in the future.  The command line API itself is
independent of whether the test suite supports additional APIs, so I
put the list of supported APIs in a new file.

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking

docs/command-line-interface.md

@@ -1,6 +1,7 @@
 # OCI Runtime Command Line Interface
 
 This file defines the OCI Runtime Command Line Interface version 1.0.0.
+It is one of potentially several [runtime APIs supported by the runtime compliance test suite](runtime-compliance-testing.md#supported-apis).
 
 ## Notation
 

docs/runtime-compliance-testing.md

@@ -0,0 +1,9 @@
+# Runtime compliance testing
+
+## Supported APIs
+
+In order to be tested for [compliance][], runtimes MUST support at least one of the following APIs:
+
+* Version 1.0.0 of the [OCI Runtime Command Line Interface](command-line-interface.md).
+
+[compliance]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc4/spec.md#notational-conventions