message: use vscode.env.openExternal.
  vscode.Uri.parse become not to call decodeURIComponent.
diff: @@ -70,10 +70,10 @@ export class Viewer {
  this.extension.logger.addLogMessage(`Cannot establish server connection.`)
  return
  }
  - // vscode.URI.parse and pdfjs viewer automatically call decodeURIComponent.
  + // pdfjs viewer automatically call decodeURIComponent.
  // So, to pass the encoded path of a pdf file to the http server,
  - // we have to call encodeURIComponent three times! 3 - 2 = 1 !
  - const url = `http://${this.extension.server.address}/viewer.html?file=/pdf:${encodeURIComponent(encodeURIComponent(encodeURIComponent(pdfFile)))}`
  + // we have to call encodeURIComponent two times! 2 - 1 = 1 !
  + const url = `http://localhost:${this.extension.server.port}/viewer.html?file=/pdf:${encodeURIComponent(encodeURIComponent(pdfFile))}`
  this.extension.logger.addLogMessage(`Serving PDF file at ${url}`)
  return url
  }
  @@ -87,7 +87,7 @@ export class Viewer {
  this.clients[pdfFile.toLocaleUpperCase()] = this.clients[pdfFile.toLocaleUpperCase()] || []
  try {
  - vscode.commands.executeCommand('vscode.open', vscode.Uri.parse(url))
  + vscode.env.openExternal(vscode.Uri.parse(url))
  this.extension.logger.addLogMessage(`Open PDF viewer for ${pdfFile}`)
  } catch (e) {
  vscode.window.showInputBox({
  