Add project files.

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

@@ -0,0 +1,13 @@
+namespace Elsa.Studio.Contracts;
+
+/// <summary>
+/// Represents a startup task that is invoked once during application startup.
+/// </summary>
+public interface IStartupTask
+{
+    /// <summary>
+    /// Invoked during application startup.
+    /// </summary>
+    /// <param name="cancellationToken">A cancellation token.</param>
+    ValueTask ExecuteAsync(CancellationToken cancellationToken = default);
+}