docs: Explain app_lib name origin (#3521)

Co-authored-by: Fabian-Lars <[email protected]>

Author: xnuwu

src/content/docs/start/project-structure.mdx

@@ -40,8 +40,8 @@ the Rust project is a normal [Cargo project](https://doc.rust-lang.org/cargo/gui
 - `build.rs` contains `tauri_build::build()` which is used for tauri's build system
 - `src/lib.rs` contains the Rust code and the mobile entry point (the function marked with `#[cfg_attr(mobile, tauri::mobile_entry_point)]`),
   the reason we don't write directly in `main.rs` is because we compile your app to a library in mobile builds and load them through the platform frameworks
-- `src/main.rs` is the main entry point for the desktop, and we run `tauri_app_lib::run()` in `main` to use the same entry point as mobile,
-  so to keep it simple, don't modify this file, modify `lib.rs` instead
+- `src/main.rs` is the main entry point for the desktop, and we run `app_lib::run()` in `main` to use the same entry point as mobile,
+  so to keep it simple, don't modify this file, modify `lib.rs` instead. Note that `app_lib` corresponds to `[lib.name]` in Cargo.toml.
 
 Tauri works similar to a static web host, and the way it builds is that you would compile your JavaScript project to static files first,
 and then compile the Rust project that will bundle those static files in,