Missing MCP Tools example for streamable-http transport

The docs for [MCP Tools](https://google.github.io/adk-docs/tools/mcp-tools/) are lacking significantly.

They do not showcase how to create toolsets for the `sse` or `streamable-http` transports, only `stdio`.

There should be an example added for streamable http at the very least as this is the recommended transport for remote MCP servers to use.

GitHub remote MCP usage example:

```python
import os
from google.adk.agents import LlmAgent
from google.adk.tools.mcp_tool import MCPToolset, StreamableHTTPConnectionParams

root_agent = LlmAgent(
model="gemini-2.5-pro-preview-06-05",
name="github_agent",
instruction="You are a helpful assistant that can answer questions about GitHub.",
tools=[
MCPToolset(
connection_params=StreamableHTTPConnectionParams(
url="https://api.githubcopilot.com/mcp/",
headers={
"Authorization": "Bearer " + os.getenv("GITHUB_PERSONAL_ACCESS_TOKEN"),
}
)
)
],
)
```