Implement opt-in experimental bandwidth saving for stickers and emojis

[dozro]

Description

I have noticed that the loading time of emojis in the emoji picker and sticker picker take a long time (at least on iPad) ... so that hopefully helps performance wise a bit...

Fixes #243 (hopefully)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings