docs: filesystems: convert coda.txt to ReST

This document has its own style. It seems to be print output
for the old matrixial printers where backspace were used to
do double prints.

For the conversion, I used several regex expressions to get
rid of some weird stuff. The patch also does almost all possible
conversions in order to get a nice output document, while keeping
it readable/editable as is:

- Add a SPDX header;
- Add a document title;
- Adjust document title;
- Adjust section titles;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Adjust list markups;
- Mark some unumbered titles with bold font;
- Use footnoote markups;
- Add table markups;
- Use notes markups;
- Add it to filesystems/index.rst.

Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Link: https://lore.kernel.org/r/25c06c40c3d7b947a131c3be124ce0e93cc00ae3.1588021877.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <[email protected]>
diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
index 373d695..ec6e308 100644
--- a/Documentation/filesystems/index.rst
+++ b/Documentation/filesystems/index.rst
@@ -63,6 +63,7 @@
    btrfs
    cifs/cifsroot
    ceph
+   coda
    cramfs
    debugfs
    dlmfs