Feat: entry sorting (#3494)

* refactor: typescript search actions, add tests avoid duplicate search

* refactor: switch from promise chain to async/await in loadEntries

* feat: add sorting, initial commit

* fix: set isFetching to true on entries request

* fix: ui improvments and bug fixes

* test: fix tests

* feat(backend-gitlab): cache local tree)

* fix: fix prop type warning

* refactor: code cleanup

* feat(backend-bitbucket): add local tree caching support

* feat: swtich to orderBy and support multiple sort keys

* fix: backoff function

* fix: improve backoff

* feat: infer sortable fields

* feat: fetch file commit metadata - initial commit

* feat: extract file author and date, finalize GitLab & Bitbucket

* refactor: code cleanup

* feat: handle github rate limit errors

* refactor: code cleanup

* fix(github): add missing author and date when traversing cursor

* fix: add missing author and date when traversing cursor

* refactor: code cleanup

* refactor: code cleanup

* refactor: code cleanup

* test: fix tests

* fix: rebuild local tree when head doesn't exist in remote branch

* fix: allow sortable fields to be an empty array

* fix: allow translation of built in sort fields

* build: fix proxy server build

* fix: hide commit author and date fields by default on non git backends

* fix(algolia): add listAllEntries method for alogolia integration

* fix: handle sort fields overflow

* test(bitbucket): re-record some bitbucket e2e tests

* test(bitbucket): fix media library test

* refactor(gitgateway-gitlab): share request code and handle 404 errors

* fix: always show commit date by default

* docs: add sortableFields

* refactor: code cleanup

* improvement: drop multi-sort, rework sort UI

* chore: force main package bumps

Co-authored-by: Shawn Erquhart <shawn@erquh.art>

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

@@ -219,10 +219,12 @@ describe('github backend implementation', () => {
   describe('entriesByFolder', () => {
     const listFiles = jest.fn();
     const readFile = jest.fn();
+    const readFileMetadata = jest.fn(() => Promise.resolve({ author: '', updatedOn: '' }));
 
     const mockAPI = {
       listFiles,
       readFile,
+      readFileMetadata,
       originRepoURL: 'originRepoURL',
     };
 
@@ -245,7 +247,7 @@ describe('github backend implementation', () => {
 
       const expectedEntries = files
         .slice(0, 20)
-        .map(({ id, path }) => ({ data: id, file: { path, id } }));
+        .map(({ id, path }) => ({ data: id, file: { path, id, author: '', updatedOn: '' } }));
 
       const expectedCursor = Cursor.create({
         actions: ['next', 'last'],
@@ -267,11 +269,13 @@ describe('github backend implementation', () => {
   describe('traverseCursor', () => {
     const listFiles = jest.fn();
     const readFile = jest.fn((path, id) => Promise.resolve(`${id}`));
+    const readFileMetadata = jest.fn(() => Promise.resolve({}));
 
     const mockAPI = {
       listFiles,
       readFile,
       originRepoURL: 'originRepoURL',
+      readFileMetadata,
     };
 
     const files = [];