doc/CodingGuidelines: URLs and paths as monospace

The current documentation uses both quotes (italics) and backquotes (monospace) to render URLs and pathnames, which is inconsistent. Document a best practice in CodingGuidelines to help reduce inconsistencies in the future. We set the best practice to using backquotes, since: * It is already an established practice. For exemple: $ git grep "'[^']/*[^']'" | wc -l 206 $ git grep '`[^`]/*[^`]`' | wc -l 690 There are false positives on both sides, but after a cursory look at the output of both, it doesn't seem the false positive rate is really higher in the second case. At least, this shows that the existing documentation uses inconsistent formatting, and that it would be good to do something about it. * It may be debatable whether path names need to be typed in monospace but having them in italics is really unusual. Signed-off-by: Corentin BOMPARD <corentin.bompard@etu.univ-lyon1.fr> Signed-off-by: Nathan BERBEZIER <nathan.berbezier@etu.univ-lyon1.fr> Signed-off-by: Pablo CHABANNE <pablo.chabanne@etu.univ-lyon1.fr> Signed-off-by: Matthieu MOY <matthieu.moy@univ-lyon1.fr> Signed-off-by: Junio C Hamano <gitster@pobox.com>