原文：获取文件的mine type类型
说一下常用的文件的mine type类型：
| MIME type | File extensions |
|---|---|
| application/msword | doc |
| application/pdf | |
| application/rtf | rtf |
| application/vnd.ms-excel | xls |
| application/vnd.ms-powerpoint | ppt |
| application/x-rar-compressed | rar |
| application/x-shockwave-flash s | wf |
| application/zip | zip |
| audio/midi | mid midi kar |
| audio/mpeg | mp3 |
| audio/ogg | ogg |
| audio/x-m4a | m4a |
| audio/x-realaudio | ra |
| image/gif | gif |
| image/jpeg | jpeg jpg |
| image/png | png |
| image/tiff | tif tiff |
| image/vnd.wap.wbmp | wbmp |
| image/x-icon | ico |
| image/x-jng | jng |
| image/x-ms-bmp | bmp |
| image/svg+xml | svg svgz |
| image/webp | webp |
| text/css | css |
| text/html | html htm shtml |
| text/plain | txt |
| text/xml | xml |
| video/3gpp | 3gpp 3gp |
| video/mp4 | mp4 |
| video/mpeg | mpeg mpg |
| video/quicktime | mov |
| video/webm | webm |
| video/x-flv | flv |
| video/x-m4v | m4v |
| video/x-ms-wmv | wmv |
| video/x-msvideo | avi |
