chore(docs): update README file

Author: omarabid

README.md

@@ -16,28 +16,42 @@ You may be looking for:
 - [Examples](examples)
 - [Release notes](https://github.com/omarabid/pyroscope/releases)
 
+## Table of Contents
+- [Quick Start](#quick-start)
+- [Limitations](#limitations)
+- [pyroscope-cli](#pyroscope-cli)
+- [Getting Help](#getting-help)
+- [License](#license)
+
 ### Quick Start
 
 Add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
 pyroscope = "0.4.0"
+pyroscope-pprofrs = "0.1"
 ```
 
-Configure your profiler:
+Configure and create the backend (pprof-rs)
+
+```rust
+let pprof_config = PprofConfig::new().sample_rate(100);
+let pprof_backend = Pprof::new(pprof_config);
+```
+
+Configure the Pyroscope agent:
 
 ```rust
  let mut agent =
      PyroscopeAgent::builder("http://localhost:4040", "myapp-profile")
-     .sample_rate(100)
+     .backend(pprof_backend)
      .build()?;
 ```
 
 Profile your code:
 
 ```rust
-
  agent.start();
  // Profiled computation
  agent.stop();
@@ -52,6 +66,8 @@ Profile your code:
 - **Timer**: epoll (for Linux) and kqueue (for macOS) are required for a more precise timer.
 - **Shutdown**: The Pyroscope Agent might take some time (usually less than 10 seconds) to shutdown properly and drop its threads.
 
+### Pyroscope CLI
+
 ### Getting help
 
 You can read the [Docs](https://docs.rs/pyroscope/) or check the [examples](examples) for detailed usage of the library. You can also join the [Slack channel](https://pyroscope.slack.com/archives/C02Q47F8LJH) if you have questions.