Bump shelljs from 0.8.3 to 0.8.5

Bumps [shelljs](https://github.com/shelljs/shelljs) from 0.8.3 to 0.8.5.
- [Release notes](https://github.com/shelljs/shelljs/releases)
- [Changelog](https://github.com/shelljs/shelljs/blob/master/CHANGELOG.md)
- [Commits](shelljs/shelljs@v0.8.3...v0.8.5)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: direct:development
...

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

Author: dependabot[bot]

package-lock.json

@@ -18,6 +18,6 @@
     "grunt-wp-i18n": "^1.0.3",
     "grunt-wp-readme-to-markdown": "^2.0.1",
     "postcss-flexibility": "^2.0.0",
-    "shelljs": "^0.8.3"
+    "shelljs": "^0.8.5"
   }
 }