This should ensure that all editors which support
https://editorconfig.org/ use 2-space indentation with spaces (not tabs)
by default.
This isn’t a full specification of the GLib coding style (see
https://gitlab.gnome.org/GNOME/gtk/blob/HEAD/docs/CODING-STYLE.md for
that), but is a correct subset of it.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>