chore: add lint-fix script

Author: brettz9

package.json

@@ -64,6 +64,7 @@
     "add-assertions": "babel-node ./src/bin/readme-assertions",
     "build": "rm -fr ./dist && NODE_ENV=production babel ./src --out-dir ./dist --copy-files --source-maps",
     "create-readme": "gitdown ./.README/README.md --output-file ./README.md && npm run add-assertions",
+    "lint-fix": "eslint --fix ./src ./test",
     "lint": "eslint ./src ./test",
     "test-cov": "BABEL_ENV=test nyc mocha --recursive --require @babel/register --reporter progress --timeout 9000",
     "test-no-cov": "BABEL_ENV=test mocha --recursive --require @babel/register --reporter progress --timeout 9000",