use yarn consistently, don't mix with npm

Author: TheSpyder

package.json

@@ -20,7 +20,7 @@
     "build": "yarn generate-tests && rescript",
     "watch": "rescript build -w",
     "test": "yarn build && yarn jest lib/js/__tests__/*_test.bs.js",
-    "generate-tests": "cd __tests__ && npx atdgen -t test.atd && npx atdgen -bs test.atd"
+    "generate-tests": "cd __tests__ && yarn exec atdgen -- -t test.atd && yarn exec atdgen -- -bs test.atd"
   },
   "devDependencies": {
     "@glennsl/rescript-jest": "^0.10.0",