Support for other office file format

[keyur-n]

First of all let me thanks to you for making such useful library, This is really nice library I found on internet which is supporting .docx, .pptx, .xlsx. While I'm curious about if you are planning for supporting other format like .doc, .ppt, .xls. Right now when selecting these files showing error that it is not supported.

This type of error for other documents.

Just let me know if there is plan for supporting other documents? or any method to convert doc to docx, ppt to pptx, xls to xlsx?