fix: upgrade node-fetch from 2.6.9 to 2.7.0

Snyk has created this PR to upgrade node-fetch from 2.6.9 to 2.7.0.

See this package in npm:
node-fetch

See this project in Snyk:
https://app.snyk.io/org/alxndrsn/project/86409bda-82ae-46df-9b25-fce1121d4538?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -51,7 +51,7 @@
     "localstorage-down": "0.6.7",
     "ltgt": "2.2.1",
     "memdown": "1.4.1",
-    "node-fetch": "2.6.9",
+    "node-fetch": "2.7.0",
     "readable-stream": "1.1.14",
     "spark-md5": "3.0.2",
     "through2": "3.0.2",