moveToNewFile: move variable under cursor

## Search Terms Move to New File Refactor Refactoring ## Suggestion Allow selecting variable name, not only function/class name, in moveToNewFile refactoring. ## Use Cases moveToNewFile is useful for refactoring React component. React component can be written in both function statements and arrow functions (function assigned to variable). But current moveToNewFile implementation requires whole lines of a variable statement to be selected, while function and class can be moved by launching Quick Fix at their name. ## Examples ```ts function Component(props: Props) { ... } ``` Currently, when placing cursor at anywhere in function or class name, i.e. `Component` in above, VSCode shows "Move to New File" menu. But if it is variable, the menu does not show up. ```ts // Cannot refactor until selecting all lines of below statement. // I want to refactor this by moving cursor to anywhere in "Component" const Component: React.FC<Props> = (props: Props) => { ... } ``` ## Checklist My suggestion meets these guidelines: * [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code * [x] This wouldn't change the runtime behavior of existing JavaScript code * [x] This could be implemented without emitting different JS based on the types of the expressions * [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.) * [x] This feature would agree with the rest of [TypeScript's Design Goals](https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals). ## Implementation https://github.com/microsoft/TypeScript/compare/master...ypresto:move-var-func-to-new-file?expand=1