Add Assay CrewAI event evidence sample

[Rul1an]

This adds Assay's small open-source CrewAI event evidence sample to the integrations list.

Why I think it fits here:

• it is a real CrewAI-focused sample, not a broad platform pitch
• it starts from CrewAI's event-listener seam
• it shows one bounded way to export task/tool runtime events and turn them into reviewable external evidence
• the sample stays explicit about not promoting CrewAI runtime semantics into Assay truth

Sample link:

• https://github.com/Rul1an/assay/tree/main/examples/crewai-event-evidence

Happy to trim the wording if you want it shorter or recategorized.

[Copilot]

Pull request overview

Adds a new community integration entry to the “Integrations” list in README.md, pointing to Assay’s open-source CrewAI event evidence sample so users can discover an example of exporting CrewAI runtime events into reviewable evidence.

Changes:

• Added a new “CrewAI + Assay Event Evidence Sample” row to the Integrations table.
• Removed a stray trailing | line at the end of the README.

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