Update docs to always use yarn add --cwd for app & backend

Some commands currently error, and others are simply formatted inconsistently.
This format seems to work and be the most popular/common,
so I applied it to all similar occurrences.

Signed-off-by: Jan Van Bruggen <JanVB@verily.com>

docs/getting-started/configure-app-with-plugins.md

@@ -22,7 +22,8 @@ to an entity in the software catalog.
 1. Add the plugin's npm package to the repo:
 
    ```bash
-   yarn workspace app add @backstage/plugin-circleci
+   # From your Backstage root directory
+   yarn add --cwd packages/app @backstage/plugin-circleci
    ```
 
    Note the plugin is added to the `app` package, rather than the root

docs/integrations/aws-s3/discovery.md

@@ -63,7 +63,7 @@ As this provider is not one of the default providers, you will first need to ins
 the AWS catalog plugin:
 
 ```bash
-# From the Backstage root directory
+# From your Backstage root directory
 yarn add --cwd packages/backend @backstage/plugin-catalog-backend-module-aws
 ```
 

docs/integrations/gerrit/discovery.md

@@ -17,7 +17,7 @@ As this provider is not one of the default providers, you will first need to ins
 the Gerrit provider plugin:
 
 ```bash
-# From the Backstage root directory
+# From your Backstage root directory
 yarn add --cwd packages/backend @backstage/plugin-catalog-backend-module-gerrit
 ```
 

docs/integrations/gitlab/discovery.md

@@ -36,7 +36,7 @@ As this provider is not one of the default providers, you will first need to ins
 the gitlab catalog plugin:
 
 ```bash
-# From the Backstage root directory
+# From your Backstage root directory
 yarn add --cwd packages/backend @backstage/plugin-catalog-backend-module-gitlab
 ```
 

docs/permissions/getting-started.md

@@ -47,7 +47,8 @@ The permissions framework uses a new `permission-backend` plugin to accept autho
 1. Add `@backstage/plugin-permission-backend` as a dependency of your Backstage backend:
 
 ```bash
-$ yarn workspace backend add @backstage/plugin-permission-backend
+# From your Backstage root directory
+$ yarn add --cwd packages/backend @backstage/plugin-permission-backend
 ```
 
 2. Add the following to a new file, `packages/backend/src/plugins/permission.ts`. This adds the permission-backend router, and configures it with a policy which allows everything.

docs/permissions/plugin-authors/01-setup.md

@@ -39,9 +39,10 @@ The source code is available here:
 
 2.  Add these packages as dependencies for your Backstage app:
 
-    ```
-    $ yarn workspace backend add @internal/plugin-todo-list-backend @internal/plugin-todo-list-common
-    $ yarn workspace app add @internal/plugin-todo-list
+    ```sh
+    # From your Backstage root directory
+    $ yarn add --cwd packages/backend @internal/plugin-todo-list-backend @internal/plugin-todo-list-common
+    $ yarn add --cwd packages/app @internal/plugin-todo-list
     ```
 
 3.  Include the backend and frontend plugin in your application:

docs/plugins/backend-plugin.md

@@ -66,7 +66,7 @@ To actually attach and run the plugin router, you will make some modifications
 to your backend.
 
 ```bash
-# From the Backstage root directory
+# From your Backstage root directory
 yarn add --cwd packages/backend @internal/plugin-carmen-backend@^0.1.1 # Change this to match the plugin's package.json
 ```
 

docs/tutorials/configuring-plugin-databases.md

@@ -37,7 +37,7 @@ package. If you intend to use both PostgreSQL and SQLite, you can install
 both of them.
 
 ```bash
-# From the Backstage root directory
+# From your Backstage root directory
 # install pg if you need PostgreSQL
 yarn add --cwd packages/backend pg