[feature request] sort by filetype

[gschintgen]

Hi,
I have some folders with a specific structure where each base filename appears with multiple extensions. Here are two examples:

• Pictures folder where images are both in .raw and in .jpg format. Seadroid shows this as
  a.jpg
  a.raw
  b.jpg
  b.raw
  etc.
• My Calibre library export has the same issue, only that 3 files share the same basename, but have different types (and extensions).

In those folders I most often only want to show or browse through one specific filetypes, e.g. the jpg's of the first example or the pdf's of the second example.

Hence my request: Please add the possibility to sort by filetype.
This is a standard feature of most other file handling programs and apps, both on desktop and mobile.