workspace/executeCommand on code fixes fails on Windows

[tomv564]

Unexpected unix-style path from typescript being fed into windows-path expecting code:

{'data': {}, 'code': -32001, 'message': 'TypeScript config file for C:/Users/tvanommeren/someproject/somefile.ts not found'}

On a request:

{ 
  title: 'Add ListItem to existing import declaration from.',
  arguments: [ { fileName: 'C:/Users/tvanommeren/someproject/somefile.ts, textChanges: [ { span: { length: 0, start: 252 }, newText: ', ListItem' } ] } ],
  command: 'codeFix' 
}