[docs-beta] update readme (#23892)

## Summary & Motivation

## How I Tested These Changes

## Changelog [New | Bug | Docs]

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examples/docs_beta_snippets/README.md

@@ -10,6 +10,7 @@ Please use the following code style to keep imports short:
 ```python
 import dagster as dg
 
+@dg.asset
 def my_cool_asset(context: dg.AssetExecutionContext) -> dg.MaterializeResult:
     return dg.MaterializeResult(
         metadata={