New sk-python-azure-functions-chatgpt-plugin and other minor updates

[raffertyuy]

Motivation, Context and Description

This pull request contains 3 contributions, sorted by complexity

1. Updated README.md of sk-python-flask-chatgpt-plugin

• Simply added instructions for running using command line.
• Previous instructions were only VSCode debugging.

2. Added HTTP GET /logo.png to sk-csharp-chatgpt-plugin

• Updated the .csproj and added Logo.cs and logo.png (using SK's logo).
• ai-plugin.json refers to this, and was previously a broken image when testing with chat-copilot

3. Adding a new sk-python-azure-functions-chatgpt-plugin

• This was my feature request in Feature Request: Python Azure Functions ChatGPT Plugin Starter #85 which I went ahead to implement.
• The code runs similar to other Azure functions using func host start.
• The complication in this code is that there is no automated generator for either openapi.yaml or swagger.json, so this had to be manually created.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel-starters/blob/main/CONTRIBUTING.md)
• The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format and python
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[raffertyuy]

@mkarle wonder if you can review this pull request?

[moonbox3]

LGTM