More samples

[FBoucher]

• Change the README file in the Getting-Started folder adding headers for easier navigation.
• Add new samples:
  • 01-Hike Summary: Summarize a long to a few words.
  • 03-Chatting About my Previous Hikes: Chat with the AI about your previous hikes.
  • 05-Hike Images: Generate postal card images to invite your friends for a hike.

[JakeRadMSFT]

Can you update:

https://github.com/dotnet/ai-samples/blob/main/README.md