docs: Document terminology used in the project

This is to be referred to by developers when working on the project, and
documents the decisions behind the terminology used.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Fixes: #13

HACKING.md

@@ -0,0 +1,22 @@
+Terminology
+-----------
+
+The main terminology used in malcontent is ‘parental controls’, which are
+implemented by ‘administrators’ and enforced on ‘child users’.
+
+The feature applies to a range of other carer/caree relationships, though, where
+the ‘caree’ user might need to be protected from doing things on the computer
+which aren’t suitable for them.
+
+The terminology ‘parental controls’ is used consistently, despite not all
+situations actually involving a parent or child, because that’s how most users
+will find the functionality.
+
+To remain as inclusive as possible, there are some rules about which terminology
+to use:
+ - Use ‘parental controls’ to refer to the overall feature
+ - Refer to ‘administrators’ or ‘administrator accounts’ rather than ‘parents’
+ - Refer to ‘child users’ in general contexts, but refer to particular user
+   accounts using their full name — don’t mention ‘child’ in that case
+
+Reference: https://gitlab.freedesktop.org/pwithnall/malcontent/-/issues/13