DOC add a contacts page

There were now a few different venues

docs/sources/contacts.md

@@ -0,0 +1,26 @@
+# Contacts
+
+How to get in touch
+
+### I have some questions comments
+
+The best is probably the [user mailing
+list](https://groups.google.com/forum/#!forum/ngless). Both developers and
+other users are there.
+
+### I want to report a bug
+
+The best is to report it using [Github
+issues](https://github.com/ngless-toolkit/ngless/issues). This way, it will not
+get lost even if everyone happens to be busy at the moment.
+
+If you are not sure if it's a bug, feel free to ask on the [user mailing
+list](https://groups.google.com/forum/#!forum/ngless) first.
+
+### I want to discuss the internals of development
+
+There are two major channels for that:
+
+- [Developer mailing list](https://groups.google.com/forum/#!forum/ngless-devel)
+- [Gitter channel](https://gitter.im/ngless-toolkit/community)
+

docs/sources/index.rst

@@ -204,4 +204,5 @@ Authors
    advanced
    Language
    Mapping
+   contacts
    software