add: Actually use gettext

src/app/rmrf.cpp

+#include <libintl.h>
+#include <locale.h>
+
 #include <iostream>
 
 #include "ui/view.hpp"
 
+#define _(str) gettext(str)
+
 int main() {
     using rmrf::ui::display;
 
+    setlocale(LC_ALL, NULL);
+    bindtextdomain("rmrf", "/usr/share/locale/");
+    textdomain("rmrf");
+
     auto h_nc = std::make_shared<display>();
 
     h_nc->sync([](const display::ptr_type &) {
-        std::cout << "Hello World!\n" << std::flush;
+        std::cout << _("Hello World!\n") << std::flush;
     });
 
     return 0;