Document `mime` for custom editor selectors

Fixes #81789

src/vs/workbench/contrib/customEditor/browser/extensionPoint.ts

@@ -53,9 +53,9 @@ const webviewEditorsContribution: IJSONSchema = {
 							type: 'string',
 							description: nls.localize('contributes.selector.filenamePattern', 'Glob that the custom editor is enabled for.'),
 						},
-						scheme: {
+						mime: {
 							type: 'string',
-							description: nls.localize('contributes.selector.scheme', 'File scheme that the custom editor is enabled for.'),
+							description: nls.localize('contributes.selector.mime', 'Glob that matches the mime type of a data uri resource.'),
 						}
 					}
 				}