Bump acorn from 6.1.1 to 7.1.0

Bumps [acorn](https://github.com/acornjs/acorn) from 6.1.1 to 7.1.0.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.1.1...7.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -26,7 +26,7 @@
 	"devDependencies": {
 		"@babel/core": "^7.3.4",
 		"@babel/preset-env": "^7.7.7",
-		"acorn": "^6.1.1",
+		"acorn": "^7.1.0",
 		"babel-eslint": "^10.0.3",
 		"babel-loader": "^8.0.6",
 		"css-loader": "^3.4.0",