docs: minor changes in preparation for merging for 2.10.0

- one sentence per line
- reference "since 2.10.0" for new features

Signed-off-by: Matthew Weier O'Phinney <matthew@weierophinney.net>

docs/book/plugin-manager.md

@@ -1,30 +1,26 @@
 # Plugin Manager
 
-The `AdapterPluginManager` extends the laminas-servicemanager
-`AbstractPluginManager`, and has the following behaviors:
+The `AdapterPluginManager` extends the laminas-servicemanager `AbstractPluginManager`, and has the following behaviors:
 
 - It will only return `Laminas\Serializer\Adapter\AdapterInterface` instances.
-- It defines short-name aliases for all shipped serializers (the class name minus
-  the namespace), in a variety of casing combinations.
+- **Since 2.10.0**: It defines short-name aliases for all shipped serializers (the class name minus the namespace), in a variety of casing combinations.
 - All services are shared by default; a new instance will only be created once and shared each time you call `get()`.
 
 ## Factory
 
-`Laminas\Serializer\AdapterPluginManager` is mapped to the factory
-`Laminas\Serializer\AdapterPluginManagerFactory` when wired to the dependency
-injection container.
+`Laminas\Serializer\AdapterPluginManager` is mapped to the factory.
+`Laminas\Serializer\AdapterPluginManagerFactory` when wired to the dependency injection container.
 
 The factory will be automatically registered when loading/installing the `Laminas\Serializer` module in `laminas-mvc` and/or loading/installing the `ConfigProvider` into a Mezzio application.
 
-The factory will look for the `config` service, and use the `serializers`
-configuration key to seed it with additional services. This configuration key
-should map to an array that follows [standard laminas-servicemanager configuration](https://docs.laminas.dev/laminas-servicemanager/configuring-the-service-manager/).
+Since version 2.10.0, the factory will look for the `config` service, and use the `serializers` configuration key to seed it with additional services.
+This configuration key should map to an array that follows [standard laminas-servicemanager configuration](https://docs.laminas.dev/laminas-servicemanager/configuring-the-service-manager/).
 
 To add your own serializer you can add the following configuration:
 
 ```php
 // config/autoload/serializers.global.php
-return [    
+return [
     'serializers' => [
         'factories' => [
             \App\MyCustomSerializer::class => \App\Container\MyCustomSerializerFactory::class,