Migrate beta to preview terminology (#61)

Author: joe4dev

README.md

@@ -1,4 +1,4 @@
-# LocalStack Extensions (beta)
+# LocalStack Extensions (Preview)
 
 <p align="center">
   <img src="https://github.com/localstack/localstack-extensions/assets/3996682/bba99a4a-e479-4da9-ba3e-1ea9ce80f9b7" alt="LocalStack Extensions">
@@ -7,7 +7,7 @@
 
 With LocalStack 1.0 we have introduced LocalStack Extensions that allow
 developers to extend and customize LocalStack. Both the feature and the API
-are currently experimental and may be subject to change.
+are currently in preview and may be subject to change.
 
 ## Using Extensions
 
@@ -25,11 +25,10 @@ $ localstack extensions --help
 
 Usage: localstack extensions [OPTIONS] COMMAND [ARGS]...
 
-  (Beta) Manage LocalStack extensions.
+  (Preview) Manage LocalStack extensions.
 
   LocalStack Extensions allow developers to extend and customize LocalStack.
-  The feature and the API are currently experimental and may be subject to
-  change.
+  The feature and the API are currently in a preview stage and may be subject to change.
 
   Visit https://docs.localstack.cloud/references/localstack-extensions/
   for more information on LocalStack Extensions.