Fix #4316: add text editor interfaces.

Oqtane.Shared/Interfaces/ITextEditorProvider.cs

@@ -0,0 +1,18 @@
+namespace Oqtane.Interfaces
+{
+    /// <summary>
+    /// Rich text editor provider interface.
+    /// </summary>
+    public interface ITextEditorProvider
+    {
+        /// <summary>
+        /// The text editor provider name.
+        /// </summary>
+        string Name { get; }
+
+        /// <summary>
+        /// The text editor type full name.
+        /// </summary>
+        string EditorType { get; }
+    }
+}