Changes after went through "Datafusion as a library section" (#1868)

* Changes after went through Datafusion as a library section

* Run prettier on library.md

Co-authored-by: Arnaud L <[email protected]>

docs/source/user-guide/library.md

@@ -19,6 +19,23 @@
 
 # Using DataFusion as a library
 
+## Create a new project
+
+```shell
+cargo new hello_datafusion
+```
+
+```shell
+$ cd hello_datafusion
+$ tree .
+.
+├── Cargo.toml
+└── src
+    └── main.rs
+
+1 directory, 2 files
+```
+
 ## Default Configuration
 
 DataFusion is [published on crates.io](https://crates.io/crates/datafusion), and is [well documented on docs.rs](https://docs.rs/datafusion/).
@@ -27,7 +44,29 @@ To get started, add the following to your `Cargo.toml` file:
 
 ```toml
 [dependencies]
-datafusion = "5.1.0"
+datafusion = "7.0.0"
+```
+
+## Create a main function
+
+Update the main.rs file with your first datafusion application based on [Example usage](https://arrow.apache.org/datafusion/user-guide/example-usage.html)
+
+```rust
+use datafusion::prelude::*;
+
+#[tokio::main]
+async fn main() -> datafusion::error::Result<()> {
+  // register the table
+  let mut ctx = ExecutionContext::new();
+  ctx.register_csv("test", "<PATH_TO_YOUR_CSV_FILE>", CsvReadOptions::new()).await?;
+
+  // create a plan to run a SQL query
+  let df = ctx.sql("SELECT * FROM test").await?;
+
+  // execute and print results
+  df.show().await?;
+  Ok(())
+}
 ```
 
 ## Optimized Configuration
@@ -37,7 +76,7 @@ worth noting that using the settings in the `[profile.release]` section will sig
 
 ```toml
 [dependencies]
-datafusion = { version = "5.0" , features = ["simd"]}
+datafusion = { version = "7.0" , features = ["simd"]}
 tokio = { version = "^1.0", features = ["rt-multi-thread"] }
 snmalloc-rs = "0.2"
 
@@ -49,12 +88,23 @@ codegen-units = 1
 Then, in `main.rs.` update the memory allocator with the below after your imports:
 
 ```rust
+use datafusion::prelude::*;
+
 #[global_allocator]
 static ALLOC: snmalloc_rs::SnMalloc = snmalloc_rs::SnMalloc;
+
+async fn main() -> datafusion::error::Result<()> {
+  ...
+}
+```
+
+Finally, in order to build with the `simd` optimization `cargo nightly` is required.
+
+```shell
+rustup toolchain install nightly
 ```
 
-Finally, in order to build with the `simd` optimization `cargo nightly` is required. Based on the instruction
-set architecture you are building on you will want to configure the `target-cpu` as well, ideally
+Based on the instruction set architecture you are building on you will want to configure the `target-cpu` as well, ideally
 with `native` or at least `avx2`.
 
 ```