readme manager initial setup (#48)

This PR makes the README ready to be managed by the readme manager. It adds custom comment tags to the readme, which are invisible when the README is rendered, but tell the readme manager where to insert and update content.

README.md

@@ -1,5 +1,9 @@
+<!--BEGIN_BANNER_IMAGE--><!--END_BANNER_IMAGE-->
+
 # 📹🎙️🦀 Rust Client SDK for LiveKit
 
+<!--BEGIN_DESCRIPTION--><!--END_DESCRIPTION-->
+
 [![crates.io](https://img.shields.io/crates/v/livekit.svg)](https://crates.io/crates/livekit)
 [![Builds](https://github.com/livekit/client-sdk-native/actions/workflows/builds.yml/badge.svg?branch=main)](https://github.com/livekit/client-sdk-native/actions/workflows/builds.yml)
 [![Tests](https://github.com/livekit/client-sdk-native/actions/workflows/tests.yml/badge.svg?branch=main)](https://github.com/livekit/client-sdk-native/actions/workflows/tests.yml)
@@ -126,3 +130,5 @@ Yes! As webrtc.rs matures, we'll eventually migrate to a pure Rust stack. For no
 - Chrome's adoption and usage means libwebrtc is thoroughly battle-tested.
 - webrtc.rs is ported from Pion (which [our SFU](https://github.com/livekit/livekit) is built on) and a better fit for server-side use.
 - libwebrtc currently supports more features like encoding/decoding and includes platform-specific code for dealing with media devices.
+
+<!--BEGIN_REPO_NAV--><!--END_REPO_NAV-->