Add large sidebar previews for text files

[icewind1991]

Before:

After:

Instead of showing a small, unreadable image of the text, we load in the full text to make it easy to quickly tell the contents of a file.
The size of the text preview is the same as the preview of (landscape) images and long texts can be scrolled.

This also adds the ability for apps to register custom thumbnails.

cc @nextcloud/designers

[jancborchardt]

Just a small detail: since it's text, it should have some margin to the sides unlile images. (My computer is in repair today, can't do it. :( Just give it the same amount of margin/padding the content below it has.)

[MorrisJobke]

Just a small detail: since it's text, it should have some margin to the sides unlile images. (My computer is in repair today, can't do it. :( Just give it the same amount of margin/padding the content below it has.)

I will do.

[MorrisJobke]

With my change it looks like this:

[jancborchardt]

Can we get rid of the excess whitespace below if the text file is short? Looks good otherwise!

[MorrisJobke]

Can we get rid of the excess whitespace below if the text file is short? Looks good otherwise!

I will give this a try.

[MorrisJobke]

I fixed it:

short text:

more text:

images:

[MorrisJobke]

👍 from me for the actual feature

[williambargent]

👍

[MariusBluem]

👍

[MariusBluem]

THX.

[jancborchardt]

Great work everyone! :)