added missing office types to extension mime type map

[alperenersoy]

hey! we have just started to use your package. thanks for that. in this pr just added some missing mime types for microsoft office extensions.

[martincivan]

@alperenersoy thank you for your contribution, released in 1.2.6

[alperenersoy]

@martincivan thanks! as i see the jpegs are mapped as image/pjpeg. are there any specific reasons for it instead of using image/jpeg?

[martincivan]

@alperenersoy I have no idea... this is how it was in the original Squirellmail plugin that I extracted the logic from.

[martincivan]

perhaps there exists some library that has these file-extension <> mime-type data more complete / in better shape, I haven't looked into it as I didn't notice any problem with this in our use-case.

[alperenersoy]

@martincivan in #19 replaced them with generic image/jpeg. and added some mime types for common extensions.