Add extra notes on files drop mime type (microsoft#180886)

Fixes microsoft#180878

Author: mjbvz

src/vscode-dts/vscode.proposed.documentPaste.d.ts

@@ -66,7 +66,11 @@ declare module 'vscode' {
 		 *
 		 * This can either be an exact mime type such as `image/png`, or a wildcard pattern such as `image/*`.
 		 *
-		 * Use `files` to indicate that the provider should be invoked if any {@link DataTransferFile files} are present in the {@link DataTransfer}..
+		 * Use `text/uri-list` for resources dropped from the explorer or other tree views in the workbench.
+		 *
+		 * Use `files` to indicate that the provider should be invoked if any {@link DataTransferFile files} are present in the {@link DataTransfer}.
+		 * Note that {@link DataTransferFile} entries are only created when dropping content from outside the editor, such as
+		 * from the operating system.
 		 */
 		readonly pasteMimeTypes: readonly string[];
 	}

src/vscode-dts/vscode.proposed.dropMetadata.d.ts

@@ -27,7 +27,11 @@ declare module 'vscode' {
 		 *
 		 * This can either be an exact mime type such as `image/png`, or a wildcard pattern such as `image/*`.
 		 *
+		 * Use `text/uri-list` for resources dropped from the explorer or other tree views in the workbench.
+		 *
 		 * Use `files` to indicate that the provider should be invoked if any {@link DataTransferFile files} are present in the {@link DataTransfer}.
+		 * Note that {@link DataTransferFile} entries are only created when dropping content from outside the editor, such as
+		 * from the operating system.
 		 */
 		readonly dropMimeTypes: readonly string[];
 	}