support js 3rd packages

[HowcanoeWang]

Otherwise, will raise the path errors when using the 3rd pure js packages:

ERROR in ./src/index.ts 29:0-32
Module not found: Error: Can't resolve 'crypto-js/md5' in '/Users/terwer/Downloads/siyuan-plugin-background-cover/src'
resolve 'crypto-js/md5' in '/Users/terwer/Downloads/siyuan-plugin-background-cover/src'
  Parsed request is a module
  using description file: /Users/terwer/Downloads/siyuan-plugin-background-cover/package.json (relative path: ./src)
    Field 'browser' doesn't contain a valid alias configuration
    resolve as module
      /Users/terwer/Downloads/siyuan-plugin-background-cover/src/node_modules doesn't exist or is not a directory
      looking for modules in /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules
        existing directory /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js
          using description file: /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/package.json (relative path: .)
            using description file: /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/package.json (relative path: ./md5)
              no extension
                /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/md5 doesn't exist
              .ts
                /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/md5.ts doesn't exist
              .scss
                /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/md5.scss doesn't exist
              as directory
                /Users/terwer/Downloads/siyuan-plugin-background-cover/node_modules/crypto-js/md5 doesn't exist
      /Users/terwer/Downloads/node_modules doesn't exist or is not a directory
      looking for modules in /Users/terwer/node_modules
        /Users/terwer/node_modules/crypto-js doesn't exist
      /Users/node_modules doesn't exist or is not a directory
      /node_modules doesn't exist or is not a directory