Update python files to have an overview comment of what the file does

[devjsc]

Prerequisites

• I checked the documentation and made sure this feature does not already exist
• I checked the existing issues to make sure this feature has not already been requested

Feature

A nice descriptive overivew/rationale for each file will give developers a clear understanding of how the framework works - it'll also benefit the fetch.ai docs team 👍

if you do (at the top, before imports)

"""
this is a top level comment, 
"""

import json
import ...

It will then be seen as the intro to the api ref in the docs:

...
a id="src.uagents.asgi"></a>

# src.uagents.asgi

this is a top level comment, it will be seen as the intro to the api ref in the docs

<a id="src.uagents.asgi.ASGIServer"></a>

## ASGIServer Objects

```python
class ASGIServer()

Additional Information (Optional)

No response