Optimize build.html page for mobiles that's displayed in /output route

[rahulkumaran]

I'm submitting a ... (check one with "x")

• [x] bug report
• [ ] feature request
• [ ] support request => Please do not submit support requests here, instead ask your query in out Gitter channel at https://gitter.im/fossasia/meilix

Actual Behaviour As you can see, everything's overlapping.

Expected Behaviour Would be really nice if we optimize it for phones.

Other information:

Minor mods to the html and css files

Would you like to work on the issue? Yes