Implement TERMINAL_DIMENSIONS op for the terminal device, CE add terminfo command

libterminal/terminal.c

@@ -5,3 +5,7 @@
 void terminal_print (const char* string, size_t len) {
   device_do ("TERMINAL", TERMINAL_PUTSTR, (void*)string, &len, NULL, NULL);
 }
+
+void terminal_dimensions (size_t* cols, size_t* rows) {
+  device_do ("TERMINAL", TERMINAL_DIMENSIONS, (void*)cols, (void*)rows, NULL, NULL);
+}