Bump npm from 6.9.0 to 6.14.6

Bumps [npm](https://github.com/npm/cli) from 6.9.0 to 6.14.6.
- [Release notes](https://github.com/npm/cli/releases)
- [Changelog](https://github.com/npm/cli/blob/latest/CHANGELOG.md)
- [Commits](https://github.com/npm/cli/compare/v6.9.0...v6.14.6)

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

package.json

@@ -26,7 +26,7 @@
     "dependencies": {
         "github-markdown-css": "^3.0.1",
         "inline-attachment": "^2.0.3",
-        "npm": "^6.9.0",
+        "npm": "^6.14.6",
         "simplemde": "^1.11.2",
         "yarn": "^1.13.0"
     }