Fixes #580. Mark Terminal.Gui.TextView as [Obsolete] in favor of gui-cs/Editor

Terminal.Gui/Views/TextInput/ContentsChangedEventArgs.cs

@@ -4,6 +4,7 @@ namespace Terminal.Gui.Views;
 ///     Event arguments for events for when the contents of the TextView change. E.g. the
 ///     <see cref="TextView.ContentsChanged"/> event.
 /// </summary>
+[Obsolete ("ContentsChangedEventArgs is obsolete because TextView is superseded by gui-cs/Editor. See https://github.com/gui-cs/Editor.", error: false)]
 public class ContentsChangedEventArgs : EventArgs
 {
     /// <summary>Creates a new <see cref="TextView.ContentsChanged"/> instance.</summary>

Terminal.Gui/Views/TextInput/TextView/TextView.cs

@@ -9,6 +9,7 @@
 ///         <listheader>
 ///             <term>Key</term> <description>Action</description>
 ///         </listheader>
+
 ///         <item>
 ///             <term>Left, Ctrl+B</term> <description>Moves the editing point left.</description>
 ///         </item>
@@ -93,8 +94,11 @@
 ///         <item>
 ///             <term>Insert</term> <description>Toggles overwrite mode.</description>
 ///         </item>
 ///     </list>
 /// </remarks>
+[Obsolete ("TextView is superseded by gui-cs/Editor's EditorView, which provides a rope-backed document model, "
+           + "cell-aware rendering, multi-caret editing, undo, syntax highlighting, folding, find/replace, and soft wrap. "
+           + "See https://github.com/gui-cs/Editor for details.", error: false)]
 public partial class TextView : View, IDesignable
 {
     /// <summary>

Terminal.Gui/Views/TextInput/TextView/TextViewAutocomplete.cs

@@ -4,6 +4,7 @@ namespace Terminal.Gui.Views;
 ///     Renders an overlay on another view at a given point that allows selecting from a range of 'autocomplete'
 ///     options. An implementation on a TextView.
 /// </summary>
+[Obsolete ("TextViewAutocomplete is obsolete because TextView is superseded by gui-cs/Editor. See https://github.com/gui-cs/Editor.", error: false)]
 public class TextViewAutocomplete : PopupAutocomplete
 {
     /// <inheritdoc/>