docs: networking: convert team.txt to ReST

Not much to be done here:
- add SPDX header;
- add a document title;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -108,6 +108,7 @@ Contents:
    switchdev
    tc-actions-env-rules
    tcp-thin
+   team
 
 .. only::  subproject and html
 

Documentation/networking/team.rst

@@ -1,2 +1,8 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====
+Team
+====
+
 Team devices are driven from userspace via libteam library which is here:
 	https://github.com/jpirko/libteam