Support Emoji Events Gitlab EventSource

[Thomasr-02]

Is your feature request related to a problem? Please describe.

Support emoji events on gitlab event source

Describe the solution you'd like

Receive webhook when is added or removed emoji config on gitlab (Issues, Merge Request,...)

Additional context

Support on this enum: https://github.com/argoproj/argo-events/blob/master/pkg/eventsources/sources/gitlab/start.go#L187

Gitlab Emoji doc

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Message from the maintainers:

If you wish to see this enhancement implemented please add a 👍 reaction to this issue! We often sort issues this way to know what to prioritize.

[Thomasr-02]

@whynowy , I'm thinking to contribute with this issue, tell me what do you think about this improvement.