[vscode] Support TextEditorOptions#indentSize added with 1.83

[rschnekenbu]

new API has been added to TextEditorOptions with 1.83:

/**
 * The number of spaces to insert when {@link TextEditorOptions.insertSpaces insertSpaces} is true.
 *
 * When getting a text editor's options, this property will always be a number (resolved).
 * When setting a text editor's options, this property is optional and it can be a number or `"tabSize"`.
 */
indentSize?: number | string;