Add missing emoji_events field support for Project Webhooks
## Add `emoji_events` support for Project Webhooks
### Description
I'm trying to configure a project webhook to receive emoji reaction events, but the Go SDK doesn't support the `emoji_events` parameter for project webhooks.
According to the [GitLab API documentation](https://docs.gitlab.com/ee/api/projects.html#add-project-hook), project webhooks support `emoji_events` since GitLab 16.0, but I cannot enable this feature when creating or updating webhooks through the Go SDK.
### Expected Behavior
I should be able to:
- Enable `emoji_events` when creating a new project webhook
- Update an existing project webhook to enable/disable `emoji_events`
- Read the `emoji_events` status when retrieving webhook information
### Current Behavior
The SDK does not provide any way to configure `emoji_events` for project webhooks. This forces me to manually configure webhooks through the GitLab UI instead of automating the setup.
### Additional Context
- Group webhooks already support `emoji_events` in the SDK
- The GitLab API supports this for both project and group webhooks
- This feature is documented in the official API docs since GitLab 16.0
### References
- [GitLab Project Webhooks API](https://docs.gitlab.com/ee/api/projects.html#add-project-hook)
- [GitLab Trigger Test Webhook](https://docs.gitlab.com/ee/api/project_webhooks/#trigger-a-test-project-webhook)
## Implementation Guide
- Read the `CONTRIBUTING.md` guide for setting up your local development environment and clone the community fork of this project.
- In `projects.go`, add a new `bool` field called `EmojiEvents` to the `ProjectHook`, `AddProjectHookOptions` and `EditProjectHookOptions` structs.
- In `projects_test.go`, ensure there is test coverage for the new field in the get, create and update project hook tests.
- Run `make reviewable` and raise an MR with your changes.
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