document the applicability of RFC 1855 / Netiquette

.gitattributes

@@ -19,3 +19,4 @@ js/test/ export-ignore
 .travis.yml export-ignore
 composer.json export-ignore
 BADGES.md export-ignore
+CODE_OF_CONDUCT.md export-ignore

CODE_OF_CONDUCT.md

@@ -0,0 +1,9 @@
+# Netiquette
+
+As suggested by the current project hoster, we are hereby referring to
+[RFC 1855](https://tools.ietf.org/html/rfc1855) as a minimum set of guidelines
+of Network Etiquette for individuals interacting on this project.
+
+The maintainers of this project reserve the right to remove unlawful or
+disrupting content and block users that repeatedly disturb the project at their
+discretion.