fix mo files needed for test not available

Hopefully gettext is in the default runner environment?

Author: kisaragi-hiu

packages/rollup-plugin-gettext/Makefile

@@ -3,9 +3,12 @@
 build:
 	npx tsc -p tsconfig.lib.json
 
+test/mo:
+	cd test && npm run compile-mo
+
 # for some reason vitest --typecheck doesn't actually fail when there are type
 # errors for me, so I'm running tsc here as a workaround
-test:
+test: test/mo
 	npx tsc
 	npx vitest run --typecheck