Bump node-red from 0.19.5 to 0.20.8

Bumps [node-red](https://github.com/node-red/node-red) from 0.19.5 to 0.20.8.
- [Release notes](https://github.com/node-red/node-red/releases)
- [Changelog](https://github.com/node-red/node-red/blob/master/CHANGELOG.md)
- [Commits](node-red/node-red@0.19.5...0.20.8)

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

Author: dependabot[bot]

package.json

@@ -11,7 +11,7 @@
   "devDependencies": {
     "coveralls": "^3.0.2",
     "mocha": "~5.2.0",
-    "node-red": "~0.19.5",
+    "node-red": "~0.20.8",
     "node-red-node-test-helper": "~0.1.8",
     "nyc": "^13.1.0"
   },