chore: import upstream snapshot with attribution

useradmin/help/gmembers.html

@@ -0,0 +1,14 @@
+<header>Members</header>
+
+The most important part of a group is the list of users who are its members.
+If a user attempts to access a file and the user is a member of the group
+that owns the file, then the group permissions for that file will apply. <p>
+
+This list does not include users who have this group as their
+<a href=group>primary group</a>, only users who have this as one of
+their <a href=2nd>secondary groups</a>. <p>
+
+If using a text box to enter group members, each username must be on a separate line. <p>
+
+<footer>
+