feat: Add EventType auto create to experimental features

[dsimansk]

Fixes #5612

Proposed Changes

• Add new experimental feature to Eventing section

/cc @pierDipi @matzew

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[psschwei]

You'll need to add a link for this content in here so it'll show up in the navigation:

docs/config/nav.yml

Lines 275 to 281 in 08f355a

	- Experimental Features:
	- About Eventing experimental features: eventing/experimental-features/README.md
	- DeliverySpec.Timeout field: eventing/experimental-features/delivery-timeout.md
	- DeliverySpec.RetryAfterMax field: eventing/experimental-features/delivery-retryafter.md
	- New Trigger Filters: eventing/experimental-features/new-trigger-filters.md
	- KReference.Group field: eventing/experimental-features/kreference-group.md
	- Knative reference mapping: eventing/experimental-features/kreference-mapping.md

[psschwei]

Looks good from a docs perspective.

/assign @pierDipi @matzew
for eventing signoff

[matzew]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dsimansk, matzew

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