message: call setGracefulCleanup() to clean up tmp files when quit.
diff: import * as vscode from 'vscode'
  import * as fs from 'fs'
  import * as path from 'path'
  -import * as tmpfs from 'tmp'
  +import * as tmpFile from 'tmp'
  import { Extension } from '../../main'
  import { PDFRenderer } from './pdfrenderer'
  import { GraphicsScaler } from './graphicsscaler'
  @@ -10,17 +10,18 @@ import { encodePath } from '../../utils/utils'
  export class GraphicsPreview {
  private cacheDir: string
  + private pdfFileInodeMap: Map<string, number>
  extension: Extension
  pdfRenderer: PDFRenderer
  graphicsScaler: GraphicsScaler
  - pdfFileInodeMap: Map<string, number>
  constructor(e: Extension) {
  this.extension = e
  this.pdfRenderer = new PDFRenderer(e)
  this.graphicsScaler = new GraphicsScaler(e)
  - const tmpdir = tmpfs.dirSync({ unsafeCleanup: true })
  + tmpFile.setGracefulCleanup()
  + const tmpdir = tmpFile.dirSync({ unsafeCleanup: true })
  this.cacheDir = tmpdir.name
  this.pdfFileInodeMap = new Map<string, number>()
  }
  