Documentation: dev-tools: Add KTAP specification

It does not make any significant additions or changes other than those
already in use in the kernel: additional features can be added as they
become necessary and used.

[1]: https://testanything.org/tap-version-13-specification.htmlSigned-off-by: Rae Moar <rmoar@google.com>
Co-developed-by: David Gow <davidgow@google.com>
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20211207190251.18426-1-davidgow@google.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/index.rst

@@ -32,6 +32,7 @@ Documentation/dev-tools/testing-overview.rst
    kgdb
    kselftest
    kunit/index
+   ktap
 
 
 .. only::  subproject and html