Updated the backend-system and frontend-system and plugins documents

Signed-off-by: Aditya Kumar <aditya.kumar60@infosys.com>

docs/backend-system/architecture/01-index.md

@@ -19,7 +19,11 @@ The diagram below provides an overview of the different building blocks, and the
 
 ![backend system building blocks diagram](../../assets/backend-system/architecture-building-blocks.drawio.svg)
 
-> NOTE: These are all concepts that existed in our old backend system in one way or another, but they have now all been lifted up to be first class concerns.
+:::note Note
+
+These are all concepts that existed in our old backend system in one way or another, but they have now all been lifted up to be first class concerns.
+
+:::
 
 ### Backend
 

docs/backend-system/architecture/03-services.md

@@ -192,7 +192,11 @@ When defining a default factory for a service, it is possible for it to end up w
 
 ## Service Factory Options
 
-> NOTE: This pattern is discouraged, only use it when necessary. If possible you should prefer to make services configurable via static configuration instead.
+:::note Note
+
+This pattern is discouraged, only use it when necessary. If possible you should prefer to make services configurable via static configuration instead.
+
+:::
 
 When declaring a service factory it's possible to include an options callback. This allows you to customize the factory through code when installing it in the backend. For example, this is how you install an explicit factory instance in the backend without any options:
 

docs/backend-system/building-plugins-and-modules/01-index.md

@@ -6,8 +6,12 @@ sidebar_label: Overview
 description: Building backend plugins and modules using the new backend system
 ---
 
-> NOTE: If you have an existing backend and/or backend plugins that are not yet
-> using the new backend system, see [migrating](./08-migrating.md).
+:::note Note
+
+If you have an existing backend and/or backend plugins that are not yet
+using the new backend system, see [migrating](./08-migrating.md).
+
+:::
 
 This section covers how to build your own backend [plugins](../architecture/04-plugins.md) and
 [modules](../architecture/06-modules.md). They are sometimes collectively referred to as

docs/frontend-system/building-plugins/02-testing.md

@@ -10,7 +10,11 @@ description: Testing plugins in the frontend system
 
 # Testing Frontend Plugins
 
-> NOTE: The new frontend system is in alpha, and some plugins do not yet fully implement it.
+:::note Note
+
+The new frontend system is in alpha, and some plugins do not yet fully implement it.
+
+:::
 
 Utilities for testing frontend features and components are available in `@backstage/frontend-test-utils`.
 

docs/plugins/backend-plugin.md

@@ -44,7 +44,11 @@ cd plugins/carmen-backend
 yarn start
 ```
 
-> Note: this documentation assumes you are using the latest version of Backstage and the new backend system. If you are not, please upgrade and migrate your backend using the [Migration Guide](../backend-system/building-backends/08-migrating.md)
+:::note Note
+
+This documentation assumes you are using the latest version of Backstage and the new backend system. If you are not, please upgrade and migrate your backend using the [Migration Guide](../backend-system/building-backends/08-migrating.md)
+
+:::
 
 This will think for a bit, and then say `Listening on :7007`. In a different
 terminal window, now run