chore: Add fetch-retry, remove isomorphic-fetch (#2297)

* chore: Add fetch-retry, remove isomorphic-fetch

closes #2270

* test: Mock fetch

package.json

@@ -73,6 +73,7 @@
     "emoji-regex": "^6.5.1",
     "es6-error": "^4.1.1",
     "exports-loader": "^0.6.4",
+    "fetch-retry": "^4.1.1",
     "fetch-with-proxy": "^3.0.1",
     "file-loader": "^1.1.6",
     "flow-typed": "^3.3.1",
@@ -86,7 +87,6 @@
     "imports-loader": "0.6.5",
     "invariant": "^2.2.2",
     "ioredis": "^4.24.3",
-    "isomorphic-fetch": "2.2.1",
     "joplin-turndown-plugin-gfm": "^1.0.12",
     "js-search": "^1.4.2",
     "json-loader": "0.5.4",
@@ -189,6 +189,7 @@
     "html-webpack-plugin": "3.2.0",
     "i18next-parser": "^3.3.0",
     "jest-cli": "^26.0.0",
+    "jest-fetch-mock": "^3.0.3",
     "koa-webpack-dev-middleware": "^1.4.5",
     "koa-webpack-hot-middleware": "^1.0.3",
     "nodemon": "^1.19.4",