chore: add timeout mechanism for fetch calls (#3649)

packages/netlify-cms-backend-github/src/__tests__/API.spec.js

@@ -117,6 +117,7 @@ describe('github API', () => {
           Authorization: 'token token',
           'Content-Type': 'application/json; charset=utf-8',
         },
+        signal: expect.any(AbortSignal),
       });
     });
 
@@ -163,6 +164,7 @@ describe('github API', () => {
           Authorization: 'promise-token',
           'Content-Type': 'application/json; charset=utf-8',
         },
+        signal: expect.any(AbortSignal),
       });
     });
   });

packages/netlify-cms-backend-github/src/__tests__/implementation.spec.js

@@ -43,6 +43,7 @@ describe('github backend implementation', () => {
         headers: {
           Authorization: 'token token',
         },
+        signal: expect.any(AbortSignal),
       });
     });
 

packages/netlify-cms-backend-github/src/implementation.tsx

@@ -28,6 +28,7 @@ import {
   runWithLock,
   blobToFileObj,
   contentKeyFromBranch,
+  unsentRequest,
 } from 'netlify-cms-lib-util';
 import AuthenticationPage from './AuthenticationPage';
 import { Octokit } from '@octokit/rest';
@@ -40,6 +41,8 @@ const MAX_CONCURRENT_DOWNLOADS = 10;
 
 type ApiFile = { id: string; type: string; name: string; path: string; size: number };
 
+const { fetchWithTimeout: fetch } = unsentRequest;
+
 export default class GitHub implements Implementation {
   lock: AsyncLock;
   api: API | null;