Add Icons to the Iconservice

[alexz707]

In the old UI are many more icons which we should add to the icon service.

https://github.com/pimcore/admin-ui-classic-bundle/blob/1.x/public/css/icons.css#L568

If it is the same icon like ppt & pptx we can just add it the the match structure.
If it should be a different icon we need to talk to UI/UX department.

Here is a list of mimetypes:
https://mimetype.io/all-types