[#10459] 📝 Update documentation to use yarn --cwd arg

Signed-off-by: LvffY <louberger@hotmail.fr>

packages/app-defaults/README.md

@@ -6,9 +6,9 @@ This package provides a default wiring of a Backstage app that avoids boilerplat
 
 Install the package via Yarn:
 
-```sh
-cd packages/app
-yarn add @backstage/app-defaults
+```bash
+# From your Backstage root directory
+yarn add --cwd packages/app @backstage/app-defaults
 ```
 
 ## Documentation

packages/backend-common/README.md

@@ -7,10 +7,9 @@ error handling and similar.
 
 Add the library to your backend package:
 
-```sh
+```bash
 # From your Backstage root directory
-cd packages/backend
-yarn add @backstage/backend-common
+yarn add --cwd packages/backend @backstage/backend-common
 ```
 
 then make use of the handlers and logger as necessary:

packages/backend-tasks/README.md

@@ -6,10 +6,9 @@ Common distributed task management for Backstage backends.
 
 Add the library to your backend package:
 
-```sh
+```bash
 # From your Backstage root directory
-cd packages/backend
-yarn add @backstage/backend-tasks
+yarn add --cwd packages/backend @backstage/backend-tasks
 ```
 
 then make use of its facilities as necessary:

packages/core-app-api/README.md

@@ -6,9 +6,8 @@ This package provides the core API used by Backstage apps.
 
 Install the package via Yarn:
 
-```sh
-cd packages/app
-yarn add @backstage/core-app-api
+```bash
+yarn add --cwd packages/app @backstage/core-app-api
 ```
 
 ## Documentation