backend-*: updated READMEs

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/pretty-icons-glow.md

@@ -0,0 +1,8 @@
+---
+'@backstage/backend-plugin-api': patch
+'@backstage/backend-dev-utils': patch
+'@backstage/backend-defaults': patch
+'@backstage/backend-app-api': patch
+---
+
+Tweaked messaging in the README.

packages/backend-app-api/README.md

@@ -1,6 +1,6 @@
 # @backstage/backend-app-api
 
-**This package is HIGHLY EXPERIMENTAL, do not use this for production**
+**This package is EXPERIMENTAL, we recommend against using it for production deployments**
 
 This package provides the core API used by Backstage backend apps.
 
@@ -17,3 +17,4 @@ yarn add --cwd packages/backend @backstage/backend-app-api
 
 - [Backstage Readme](https://github.com/backstage/backstage/blob/master/README.md)
 - [Backstage Documentation](https://github.com/backstage/backstage/blob/master/docs/README.md)
+- [Backstage Backend System](https://backstage.io/docs/backend-system/)

packages/backend-defaults/README.md

@@ -1,8 +1,8 @@
 # @backstage/backend-defaults
 
-**This package is HIGHLY EXPERIMENTAL, do not use this for production**
+**This package is EXPERIMENTAL, we recommend against using it for production deployments**
 
-This package provides the core API used by Backstage backend apps.
+This package provides the default implementations and setup for a standard Backstage backend app.
 
 ## Installation
 
@@ -17,3 +17,4 @@ yarn add --cwd packages/backend @backstage/backend-defaults
 
 - [Backstage Readme](https://github.com/backstage/backstage/blob/master/README.md)
 - [Backstage Documentation](https://github.com/backstage/backstage/blob/master/docs/README.md)
+- [Backstage Backend System](https://backstage.io/docs/backend-system/)

packages/backend-dev-utils/README.md

@@ -1,5 +1,20 @@
-# backend-dev-utils
+# @backstage/backend-dev-utils
 
-Welcome to the backend-dev-utils package!
+**This package is EXPERIMENTAL, but we encourage use of it to add support for the new backend system in your own plugins**
 
-_This package is experimental._
+This package helps set up local development environments for Backstage backend packages.
+
+## Installation
+
+Add the library to your backend plugin or module package:
+
+```bash
+# From your Backstage root directory
+yarn add --cwd plugins/<plugin>-backend @backstage/backend-dev-utils
+```
+
+## Documentation
+
+- [Backstage Readme](https://github.com/backstage/backstage/blob/master/README.md)
+- [Backstage Documentation](https://github.com/backstage/backstage/blob/master/docs/README.md)
+- [Backstage Backend System](https://backstage.io/docs/backend-system/)

packages/backend-plugin-api/README.md

@@ -1,19 +1,20 @@
 # @backstage/backend-plugin-api
 
-**This package is HIGHLY EXPERIMENTAL, do not use this for production**
+**This package is EXPERIMENTAL, but we encourage use of it to add support for the new backend system in your own plugins**
 
-This package provides the core API used by Backstage backend plugins.
+This package provides the core API used by Backstage backend plugins and modules.
 
 ## Installation
 
-Add the library to your backend plugin package:
+Add the library to your backend plugin or module package:
 
 ```bash
 # From your Backstage root directory
-yarn add --cwd plugin/<plugin>-backend @backstage/backend-plugin-api
+yarn add --cwd plugins/<plugin>-backend @backstage/backend-plugin-api
 ```
 
 ## Documentation
 
 - [Backstage Readme](https://github.com/backstage/backstage/blob/master/README.md)
 - [Backstage Documentation](https://github.com/backstage/backstage/blob/master/docs/README.md)
+- [Backstage Backend System](https://backstage.io/docs/backend-system/)