message: Improve type for (local)rootFiles
diff: @@ -10,8 +10,8 @@ import {Extension} from '../main'
  export class Manager {
  extension: Extension
  - rootFiles: object
  - localRootFiles: object
  + rootFiles: { [key: string]: string }
  + localRootFiles: { [key: string]: string | undefined }
  workspace: string
  texFileTree: { [id: string]: Set<string> } = {}
  fileWatcher: chokidar.FSWatcher
  