docs(contributing.md): add a comment to make good use of `rust-analyz…

…er` (#3388)

CONTRIBUTING.md

@@ -4,18 +4,26 @@ You want to contribute? You're awesome! Don't know where to start? Check the [li
 
 [easy tag]: https://github.com/hyperium/hyper/issues?q=label%3AE-easy+is%3Aopen
 
-
 ## [Pull Requests](./docs/PULL_REQUESTS.md)
 
 - [Submitting a Pull Request](./docs/PULL_REQUESTS.md#submitting-a-pull-request)
 - [Commit Guidelines](./docs/COMMITS.md)
 
 ## Cargo fmt
+
 `cargo fmt --all` does not work in hyper. Please use the following commands:
+
 ```txt
 # Mac or Linux
 rustfmt --check --edition 2018 $(git ls-files '*.rs')
 
 # Powershell
 Get-ChildItem . -Filter "*.rs" -Recurse | foreach { rustfmt --check --edition 2018 $_.FullName }
-```
+```
+
+> **NOTE**: If you are using `rust-analyzer`, you can add the following two lines in your `settings.json` to make sure the features get taken into account when checking the project:
+>
+>    ```json
+>     "rust-analyzer.cargo.features": ["full"],
+>     "rust-analyzer.check.features": ["full"],
+>    ```