72 update custom apps to be compatible with new launch sequence

[BPerlakiH]

• Update the common story board for custom apps.
• Update their info.json data, to include the welcomeLogo width and height.
• Update the README

[BPerlakiH]

The DWDS app also needs the loading text localised (DE):

"welcome.loading.data.text" = "Loading Data...";

[BPerlakiH]

This is good to go, in cooperation with kiwix/kiwix-apple#1008 gives the desired outcome for custom apps.

[kelson42]

@BPerlakiH Image width and height should be retrieved from the image file itself. This is fully redondant and source of error to have to specify it in the json.

[BPerlakiH]

@BPerlakiH Image width and height should be retrieved from the image file itself. This is fully redondant and source of error to have to specify it in the json.

@kelson42 Yes, you are right. I have updated it so we get the size during runtime here: kiwix/kiwix-apple#1019