feat(dev-dekstop): explain user shell customization 📝

Author: meysam81

src/infra/docs/dev-desktop.md

@@ -70,6 +70,19 @@ git config --global user.name "Your name"
 git config --global user.email "your-email"
 ```
 
+## How to customize your shell
+
+You can configure your default shell by opening a pull request against the
+[Simpleinfra ansible] to modify the `vars_user_config` as shown bloe:
+
+```yaml
+vars_user_config:
+  - username: gh-jdno
+    shell: /usr/bin/zsh
+  - username: gh-WaffleLapkin
+    shell: /usr/bin/fish
+```
+
 ## How to install a Rust toolchain
 
 The dev desktops don’t have Rust pre-installed, but instead make it easy to
@@ -157,4 +170,5 @@ We might ask you to create an issue in the [rust-lang/simpleinfra] repository.
 [rust-lang/rust]: https://github.com/rust-lang/rust
 [rust-lang/simpleinfra]: https://github.com/rust-lang/simpleinfra
 [visual studio code]: https://code.visualstudio.com/
-[certain teams]: https://github.com/search?q=repo%3Arust-lang%2Fteam+path%3Ateams%2F*.toml+dev-desktop&type=code&ref=advsearch
+[certain teams]: https://github.com/search?q=repo%3Arust-lang%2Fteam+path%3Ateams%2F*.toml+dev-desktop&type=code&ref=advsearch
+[Simpleinfra ansible]: https://github.com/rust-lang/simpleinfra/blob/dbf839ef25155df1f33c18f151283436b0f70f3b/ansible/roles/dev-desktop/defaults/main.yml#L12:L16