Add docs on how to use snippets (#1604)

src/Snippets/README.md

@@ -5,3 +5,26 @@ Various code-snippets used in the Polly documentation. Run the following command
 ```powershell
 dotnet mdsnippets
 ```
+
+Visit <https://github.com/SimonCropp/MarkdownSnippets> for more details.
+
+## How to use snippets in Polly documentation
+
+First, locate the relevant `.cs` file where the snippet resides. For instance, `retry.md` refers to snippets found in the `Retry.cs` file.
+
+Next, set up your code snippet. Ideally, use a new method and enclose the section you want to reference between `#region my-snippet` and `#endregion` tags.
+
+```csharp
+public static void MySnippet()
+{
+    #region my-snippet
+
+    // your code here
+
+    #endregion
+}
+```
+
+In your markdown documentation, refer to your code snippet by adding `<!-- snippet: my-snippet -->` and `<!-- endSnippet -->` comments to your markdown file.
+
+To conclude, run the `dotnet mdsnippets` command from the root directory to refresh snippets throughout all markdown files.