Dropping a file does not show "dropzone"

[tbsbdr]

Steps to reproduce

1. login to https://ocis.ocis-web.latest.owncloud.works
2. You are in "Personal"
3. drag some files from you local system over the #main section
4. I don't get feedback if I can now release (drop) the files at the current position of my mouse pointer

Expected behaviour

• files can get dropped, if mouse is over the #main section
• Show a blue-transparent dropzone, if files can get dropped
• Note: drop zone bg-color is different in light and dark; find exact values here: https://www.figma.com/file/EqAiB1wY7cYaMaitjyzup3/Current-oC-Web-UI-Kit-(WIP)?node-id=2016%3A219284

Actual behaviour

• I don't get feedback if I can now release (drop) the files at the current position of my mouse pointer

relates to #7081

[tbsbdr]

fyi @lookacat other than discussed I decided to show the blue dropzone all over the main area (and not only on the fileslist). seemed more straight forward to me.

[tbsbdr]

@kulmann thinking of making this a GA-Blocker as UX is really bad if there is no feedback and drag and drop is often used. 

currently there is no feedback at all that uploading via drag and drop is possible.

do you agree?

[kulmann]

@kulmann thinking of making this a GA-Blocker as UX is really bad if there is no feedback and drag and drop is often used. 

currently there is no feedback at all that uploading via drag and drop is possible.

do you agree?

Agreed. There is an open PR already (not finished, yet), see #7251