Enhancement: Allow to remove (selected)unused flag images and language files to reduce app size

Hi,

Could you add a feature which allows you to choose which countries you require? Something like the Custom Master List but it should remove the flag images and language files that are not required.
I checked and found that the unused flag images and language xml files add a little more than 500kb to the app size. If these could be removed by the developer somehow it would be great.

Thanks

No files or tests are named in the issue. Start by locating the existing Custom Master List implementation and the flag-image and language-XML resources; done means developers can select required countries and the unused resources are excluded from the app build.

索引モデルが issue の本文から書いたものです。