chore: Run standard in pretest lifecycle (yargs#1140)

Static analysis should be done before tests. It saves times and also lints and catches errors through static analysis in tests.

package.json

@@ -42,7 +42,7 @@
     "yargs-test-extends": "^1.0.1"
   },
   "scripts": {
-    "posttest": "standard",
+    "pretest": "standard",
     "test": "nyc --cache mocha --require ./test/before.js --timeout=8000 --check-leaks",
     "coverage": "nyc report --reporter=text-lcov | coveralls",
     "release": "standard-version"