docs: Update --emoji-reactions Documentation

[Len4i]

what

Github allowing only specific emojis to be sent as reaction and thumbsup is not on of them
can be +1 instead according to their list, didn't test it personally

why

Documentation is not accurate. I've spent some time trying to understand why emoji is not working

references

Link to github documentation

• Fixes thumbsup and thumbsdown are no longer valid emoji reactions in GitHub #4842

[X-Guardian]

Can you also add a link to the Gitlab emoji list to your change: https://gitlab.com/gitlab-org/gitlab/-/blob/master/fixtures/emojis/digests.json

[Len4i]

Can you also add a link to the Gitlab emoji list to your change: https://gitlab.com/gitlab-org/gitlab/-/blob/master/fixtures/emojis/digests.json

Sure! I was trying to find this list in their documentation by myself but had no luck.
Added link, thank you

[Len4i]

@X-Guardian looks like muffet check is failing on the Join us on Slack button. Probably something changed in the cncf slack. It's not urgent for me to merge this PR, just wanted to bring awareness, probably it will affect other PRs as well

[X-Guardian]

The https://communityinviter.com/ website that we link to in the docs is down, and has been for at least 24 hours. Nothing to do with your changes. I'll see if I can get the 'Website Link Check' removed from the list of required checks, as it makes no sense to block PRs being merged in this situation.