docs: cdrom: convert docs to ReST and rename to *.rst

The stuff there is almost already at ReST format. A
conversion for them is trivial: just add a missing titles
and fix some scape codes for them to match ReST syntax.

While here, rename the cdrom-standard.txt, with was converted
from LaTeX to ReST on the previous patch, and add it to the
index file.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

drivers/block/Kconfig

@@ -347,7 +347,7 @@ config CDROM_PKTCDVD
 	  is possible.
 	  DVD-RW disks must be in restricted overwrite mode.
 
-	  See the file <file:Documentation/cdrom/packet-writing.txt>
+	  See the file <file:Documentation/cdrom/packet-writing.rst>
 	  for further information on the use of this driver.
 
 	  To compile this driver as a module, choose M here: the