title: How to select folder or files using electron dialog?
body: <p>I want to be able to select either whole directory or multi or single files.</p>
  
  <p>I am able to select only one type so file or directory depending what options i use when creating the dialog box. I know I can create two separate option to either select folder or files but it'd be more handy to have it in one dialog box. </p>
  
  <pre><code>//opens dialog window
  var selectStl = () =&gt; {
      dialog.showOpenDialog({
          title: "Choose STL Models",
          buttonLabel: "Choose Files",
          defaultPath: app.getPath("desktop"),
          properties: ["multiSelections", "openFile", "openDirectory"],
          filters: [
              {name: 'stl', extensions: ['stl']}
          ]
      }, filepath =&gt; {
          filepath.forEach(filePath =&gt; {
              if(filePath.includes(".stl") || filePath.includes(".STL")){
                  stlList.innerHTML += `&lt;option&gt;${filePath}&lt;/option&gt;`;
              }else{
                  fs.readdir(filePath, (err, files) =&gt;{
                      files.forEach(file =&gt; {
                          if(file.includes(".stl") || file.includes(".STL")){
                              var path = filePath + "\\" + file;
                              stlList.innerHTML += "&lt;option&gt;" + path + "&lt;/option&gt;";
                          }
                      })
                  })
              }           
          })
      })
  }
  </code></pre>
  
  <p>Expected: Should be able to select folder or if I open the folder the files in it.</p>
  
  <p>Actual: I can select directory but if I go into it the files don't appear. Seems like the "openDirectory" property gets more priority.</p>