Update readme to include agents sdk example

[1egoman]

There's not a ton I added here, but I think this at least starts to point users in the direction of agents in the readme versus what was there previously.

Merging blocked on #1207 and broader docs updates (link placeholders need to be replaced with the eventual docs link urls)

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size-limit report 📦

Path	Size
LiveKitRoom only	6 KB (0%)
LiveKitRoom with VideoConference	30.59 KB (0%)
All exports	38.6 KB (0%)

[1egoman]

This is another place the eventual TokenSource docs from here should be linked: livekit/client-sdk-js#1681

[xianshijing-lk]

lgtm, assuming you will address the comments, no need to wait for my second look

[xianshijing-lk]

Idea: by looking at the doc today, it seems Video Conference Quick Start is under Agent SDK Example, while I think they should be separate sections.

Does it make sense to have 1, 2 to distinguish the session that they are for different use cases like

1. Agent SDK Example

2. Video Conference Quick Start