Add project files.

src/framework/Elsa.Studio.Core/Contracts/IWidgetRegistry.cs

@@ -0,0 +1,17 @@
+namespace Elsa.Studio.Contracts;
+
+/// <summary>
+/// Provides a registry of widgets.
+/// </summary>
+public interface IWidgetRegistry
+{
+    /// <summary>
+    /// Adds the specified widget to the registry.
+    /// </summary>
+    void Add(IWidget widget);
+    
+    /// <summary>
+    /// Returns a list of widgets for the specified zone.
+    /// </summary>
+    IEnumerable<IWidget> List(string zone);
+}