[Global Menu] Set translation domain

Ensures `i18n` in C++ side of things works (cherry picked from commit 42efa49b)

[Global Menu] Set translation domain
Ensures `i18n` in C++ side of things works (cherry picked from commit 42efa49b)
b2134918 · Kai Uwe Broulik · 232ede04 · b2134918
Commit b2134918 authored Dec 09, 2021 by Kai Uwe Broulik 🍇
--- a/applets/appmenu/CMakeLists.txt
+++ b/applets/appmenu/CMakeLists.txt
+add_definitions(-DTRANSLATION_DOMAIN=\"plasma_applet_org.kde.plasma.appmenu\")
+
 add_subdirectory(lib)
 add_subdirectory(plugin)