docs/sp_SP: Add process email-clients translation

Translate the following document into Spanish:

- process/email-clients.rst
Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Link: https://lore.kernel.org/r/20230117144722.31195-1-carlos.bilbao@amd.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/sp_SP/process/index.rst

@@ -15,3 +15,4 @@
    coding-style
    code-of-conduct
    kernel-enforcement-statement
+   email-clients