Update referers.yml

[torpedo89]

Add new Section for AI Chatbot Providers and added the most well-known providers to this section

[stanch]

Hey @torpedo89, just a quick note that this PR is not forgotten, but it will take us some time to roll this out. Unfortunately, for historical reasons, the referrer types are hardcoded in the Scala refer parser library which Enrich uses. So this also requires a change in that library, plus a new release of Enrich (and Snowplow Mini and Micro), plus it needs to be rolled out for everyone who is using a config file updated as per this PR.

[AlexBenny]

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[AlexBenny]

Closing in favour of #245