message: Add .dtx file type while inferring a language ID
diff: @@ -280,6 +280,8 @@ export class Manager implements IManager {
  return 'jlweave'
  } else if (this.rsweaveExt.includes(ext)) {
  return 'rsweave'
  + } else if (ext === '.dtx') {
  + return 'doctex'
  } else {
  return undefined
  }
  