Add commented i18n.merge_file version

Using that makes use of gettext (and msgfmt) rather than intltool,
which is the proper way but requires a more recent gettext version and
I'm not comfortable adding that dependency for now.

Specifically, it would require updating the autotools chain as well
as the template files are incompatible.

See https://wiki.gnome.org/MigratingFromIntltoolToGettext for more info.

packages/meson.build

@@ -8,6 +8,17 @@ else
                                       output: 'aegisub.desktop.template',
                                       configuration: c_pkg)
 
+    # TODO: switch this to gettext from intltool
+    #       requires modifying the autotools chain and a recent-ish gettext
+    #       https://wiki.gnome.org/MigratingFromIntltoolToGettext
+    #
+    # i18n = import('i18n')
+    # i18n.merge_file(input: desktop_template,
+    #                 output: 'aegisub.desktop',
+    #                 type: 'desktop',
+    #                 po_dir: '../po',
+    #                 install: true,
+    #                 install_dir: join_paths(get_option('datadir'), 'applications'))
     intltool_merge = find_program('intltool-merge')
     desktop = custom_target('aegisub.desktop',
                             input: desktop_template,