Allow catalogue to be re-indexed periodically

[flowfalls]

Is your feature request related to a problem? Please describe.
Please add functionality to run the reindex() periodically. I need to have my customers know up-to-date information in regards to stock-levels.

Describe the solution you'd like
I'd like it to easily run the reindex() job; just as we do with the admin-ui button but removing the manual process.

Describe alternatives you've considered
I've had to use axios to login to the backend and make a graphql post in order to run the reindex via a cron job.

Additional context
current rudimentary solution:

@Cron(CronExpression.EVERY_10_SECONDS)
   async routineReindexing() {
       if (this.processContext.isWorker) {

           const jar = new CookieJar();
           const client = wrapper(axios.create({jar} as AxiosRequestConfig));

           await client({
               url: 'http://localhost:3000/admin-api',
               method: 'post',
               data: {
                   operationName: "AttemptLogin",
                   variables: {
                       "username": config.authOptions.superadminCredentials?.identifier,
                       "password": config.authOptions.superadminCredentials?.password,
                       "rememberMe": false
                   },
                   query: "mutation AttemptLogin($username: String!, $password: String!, $rememberMe: Boolean!) {\n  login(username: $username, password: $password, rememberMe: $rememberMe) {\n    ...CurrentUser\n    ...ErrorResult\n    __typename\n  }\n}\n\nfragment CurrentUser on CurrentUser {\n  id\n  identifier\n  channels {\n    id\n    code\n    token\n    permissions\n    __typename\n  }\n  __typename\n}\n\nfragment ErrorResult on ErrorResult {\n  errorCode\n  message\n  __typename\n}\n"

               }
           }).catch((reason => console.log(reason)));

           await client({
               url: 'http://localhost:3000/admin-api',
               method: 'post',
               withCredentials: true,
               data: {
                   query: `
                     mutation Reindex {
                         reindex {
                           id
                         }
                       }
                     `,
               },
           }).then((result) => {
               console.log(result.data)
           }).catch((reason => console.log(reason)));
       }

[michaelbromley]

Relates to #1425 - the same mechanism discussed in that issue would be used to handle this use-case too.