Bump semver from 5.5.0 to 6.2.0

Bumps [semver](https://github.com/npm/node-semver) from 5.5.0 to 6.2.0.
- [Release notes](https://github.com/npm/node-semver/releases)
- [Changelog](https://github.com/npm/node-semver/blob/master/CHANGELOG.md)
- [Commits](npm/node-semver@v5.5.0...v6.2.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

package-lock.json

@@ -64,7 +64,7 @@
     "postcss-loader": "^2.0.8",
     "postcss-url": "^7.2.1",
     "rimraf": "^2.6.0",
-    "semver": "^5.3.0",
+    "semver": "^6.2.0",
     "shelljs": "^0.7.6",
     "uglifyjs-webpack-plugin": "^1.1.1",
     "url-loader": "^0.5.8",