Add blitterblatter poem endpoint to the skillset example

[Copilot]

This PR adds a new endpoint to our skillset example that generates a poem about "blitterblatter" as requested in the issue.

Changes:

• Created a new handler function in handlers/poem.go that returns a pre-written poem about blitterblatter
• Added a route for /random-poem in main.go to serve the poem
• Updated README.md to include documentation about the new endpoint
• Added this skill to the set of examples for users to try

The new endpoint can be invoked by:

@skillset-example write a poem about blitterblatter

When configuring the skillset in GitHub, add:

Name: random_poem
Inference description: Generates a poem about blitterblatter
URL: https://<your ngrok domain>/random-poem
Parameters: { "type": "object" }
Return type: String

Fixes #19.