feat(backend-github): GitHub GraphQL API support (#2456)

* add GitHub GraphQL api initial support

* support mutiple backends for e2e tests - initial commit

* add github backend e2e test (currently skipped), fix bugs per tests

* refactor e2e tests, add fork workflow tests, support fork workflow in GraphQL api

* remove log message that might contain authentication token

* return empty error when commit is not found when using GraphQL (align with base class)

* disable github backend tests

* fix bugs introduced after rebase of GraphQL and OpenAuthoring features

* test: update tests per openAuthoring changes, split tests into multiple files

* fix: pass in headers for pagination requests, avoid async iterator as it requires a polyfill on old browsers

* test(e2e): disable github backend tests

packages/netlify-cms-backend-github/package.json

@@ -17,10 +17,17 @@
   "scripts": {
     "develop": "yarn build:esm --watch",
     "build": "cross-env NODE_ENV=production webpack",
-    "build:esm": "cross-env NODE_ENV=esm babel src --out-dir dist/esm --ignore **/__tests__ --root-mode upward"
+    "build:esm": "cross-env NODE_ENV=esm babel src --out-dir dist/esm --ignore **/__tests__ --root-mode upward",
+    "createFragmentTypes": "node scripts/createFragmentTypes.js"
   },
   "dependencies": {
+    "apollo-cache-inmemory": "^1.6.2",
+    "apollo-client": "^2.6.3",
+    "apollo-link-context": "^1.0.18",
+    "apollo-link-http": "^1.5.15",
     "common-tags": "^1.8.0",
+    "graphql": "^14.4.2",
+    "graphql-tag": "^2.10.1",
     "js-base64": "^2.5.1",
     "semaphore": "^1.1.0"
   },