Add GitHub Action to regularly check unicode emoji are up to date with those in server

[neiljp]

These change infrequently, but it would be useful to be alerted when these need to be updated.

We have a script which fetches and converts the emoji right now, which should allow this to be automated fairly easily.

[Ezio-Sarthak]

Would love to automate this :)

[Ezio-Sarthak]

@zulipbot claim

[zulipbot]

Hello @Ezio-Sarthak!

Thanks for your interest in Zulip! You have attempted to claim an issue without the labels "help wanted", "good first issue". Since you're a new contributor, you can only claim and submit pull requests for issues with the help wanted or good first issue labels.

If this is your first time here, we recommend reading our guide for new contributors before getting started.

[zulipbot]

Hello @zulip/server-emoji members, this issue was labeled with the "area: emoji" label, so you may want to check it out!