fix: deps/npm/docs/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-CIPHERBASE-12084814
- https://snyk.io/vuln/SNYK-JS-SHAJS-12089400

Author: snyk-bot

deps/npm/docs/package.json

@@ -11,7 +11,7 @@
   "dependencies": {
     "babel-plugin-styled-components": "^1.10.6",
     "eslint": "^6.3.0",
-    "gatsby": "^2.18.17",
+    "gatsby": "^2.20.21",
     "gatsby-image": "^2.2.37",
     "gatsby-plugin-catch-links": "^2.1.21",
     "gatsby-plugin-ipfs": "^2.0.2",