"Tux Paint (Fullscreen)" launcher for Freedesktop.org

Adding a separate launcher that runs "tuxpaint --fullscreen=native"
for XDG environments (e.g., Linux); similar to what we have for
Windows.

Closes https://sourceforge.net/p/tuxpaint/feature-requests/227/
h/t Aaron

src/po/ff.po

@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: tuxpaint\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2023-03-30 09:13-0700\n"
+"POT-Creation-Date: 2023-04-01 16:47-0700\n"
 "PO-Revision-Date: 2017-12-03 10:35+0200\n"
 "Last-Translator: Ibrahima SARR <ibrahima.sarr@pulaagu.com>\n"
 "Language-Team: FULAH LOCALIZATION\n"
@@ -331,6 +331,7 @@ msgid "Tux Paint"
 msgstr "Tux Paint"
 
 #: ../org.tuxpaint.Tuxpaint.appdata.xml.in:9 ../tuxpaint.desktop.in:10
+#: ../tuxpaint-fullscreen.desktop.in:10
 msgid "A drawing program for children"
 msgstr "Topirde natgol nde sukaaɓe mbaɗanaa"
 
@@ -1378,10 +1379,14 @@ msgid ""
 "tone), and black (to shade), to mix together a new color."
 msgstr ""
 
-#: ../tuxpaint.desktop.in:9
+#: ../tuxpaint.desktop.in:9 ../tuxpaint-fullscreen.desktop.in:9
 msgid "Drawing program"
 msgstr "Topirde natgol"
 
+#: ../tuxpaint-fullscreen.desktop.in:3
+msgid "Tux Paint (Fullscreen)"
+msgstr ""
+
 #: ../../magic/src/alien.c:67
 msgid "Color Shift"
 msgstr "Baylugol Goobol"