The tips are not enabled in Translations/locale.xml yet, because the
font currently used to display them in FlightGear's splash screen
doesn't have the required glyphs (see [1] for more details). Better
display English tips than empty rectangles on the startup screen.
Merging this in disabled state now has a few advantages compared to
waiting for the font problem to be solved:
- avoid that someone ignoring the merge request[1] duplicates the
translation work;
- allow easy updating of these tips;
- make sure they aren't forgotten when FG's localization files are
converted to XLIFF format.
Ship an empty Translations/zh_CN/options.xml, otherwise
'fgfs --language=zh_CN --help --verbose' won't work at all.
[1] https://sourceforge.net/p/flightgear/fgdata/merge-requests/92/
