Bump yargs from 14.2.0 to 15.0.2

Bumps [yargs](https://github.com/yargs/yargs) from 14.2.0 to 15.0.2.
- [Release notes](https://github.com/yargs/yargs/releases)
- [Changelog](https://github.com/yargs/yargs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/yargs/yargs/compare/v14.2.0...v15.0.2)

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

package.json

@@ -102,7 +102,7 @@
     "webpack-cli": "^3.3.2",
     "webpack-dev-middleware": "^3.6.2",
     "webpack-dev-server": "^3.3.1",
-    "yargs": "^14.2.0"
+    "yargs": "^15.0.2"
   },
   "eslintConfig": {
     "extends": "openlayers",