Add a "Running locally" section to the README file

README.md

@@ -137,6 +137,25 @@ Alternatively, you can also post your question on [Gitter](https://app.gitter.im
 
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+## Running locally
+
+This project uses the newer `.slnx` format instead of the traditional `.sln` file. You can open it using **Visual Studio 2022** or newer.
+
+> [!TIP]
+> If you encounter the following error when trying to open the `.slnx` file:
+>
+> > The selected file is not a valid solution file.
+>
+> It's likely that the **Solution File Persistence Model** feature needs to be enabled. To do this:
+>
+> 1. Open **Visual Studio**.
+> 2. Go to **Tools > Options**.
+> 3. In the left-hand menu, select **Environment > Preview Features**.
+> 4. Enable the checkbox for **Use Solution File Persistence Model**.
+> 5. Click **OK** and restart Visual Studio.
+>
+> Once the solution file opens, you can set the desired project as the **Startup Project** (right-click on the project > *Set as Startup Project*) and start debugging or running as usual.
+
 ## Nightly builds
 
 If you want to try out the latest features and bug fixes, there is a MyGet feed with nightly builds of OpenIddict.