restrict file types in HTML upload code example

Example 1: input limit file type html

<!-- (IE 10+, Edge (EdgeHTML), Edge (Chromium), Chrome, Firefox 42+) -->
<input type="file" accept=".jpg,.png,.pdf" />

Example 2: file type input limit in html

<!-- Right approach: Use both file extensions and corresponding MIME-types. -->
<!-- (IE 10+, Edge (EdgeHTML), Edge (Chromium), Chrome, Firefox) -->
<input type="file"
 accept=".xls,.xlsx, application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,application/vnd.ms-excel" />