FEAT: Make SSE easier

There is friction when using SSE with Air. While we have a good SSEResponse for the backend, the client remains obtuse. Per https://htmx.org/extensions/sse/ you have to:

1. Use an `air.Script` to import the SSE extension to match this HTML spec:

```python

```

2. The tag to be modified then has to have these controls

```html

**Describe the feature**

Some kind of wrapper around all of the above would be useful. Something like this might be the way:

```python
air.Div(
# The following line would:
# prepend the current tag with the SSE import:
#
# and would generate these attributes:
# hx-ext="sse"
# sse-connect="/chatroom"
sse="/chatroom",
# Generates a hx-swap attribute per the SSE extention docs
sse_swap=""
)
```

Start by reviewing the existing SSEResponse and air.Script APIs, then compare the proposed air.Div usage with the linked htmx SSE extension requirements. Done means agreeing on and implementing a wrapper that covers the SSE import and connection, extension, and swap attributes described in the issue.

Written by the indexing model from the issue text.