API: Document limitations for the event_type length of the repository_dispatch event

[bandantonio]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

Create a repository dispatch event: Parameters

What part(s) of the article would you like to see updated?

Add a note telling that the event_type value is limited to 100 characters.

Additional information

{
    "message": "Invalid request.\n\nOnly 100 characters are allowed; 101 were supplied.",
    "documentation_url": "https://docs.github.com/rest/reference/repos#create-a-repository-dispatch-event"
}

Related issue: #15710

[docubot]

Thank you for opening this issue! Updates to the REST/GraphQL API description must be made internally. I have copied your issue to an internal issue, so I will close this issue.