Add possibility to toggle the high contrast mode

[steffenkleinle]

Is your feature request related to a problem? Please describe.
As a visibly impaired person I want to be able to still use the app. For this reason we want to introduce a new high contrast mode. We need a way to enable and disable this high contrast mode.

Describe the solution you'd like
TBD, possible options: New button/switch in the toolbar or header (:warning: this would only be visible once a city is selected).

Describe alternatives you've considered
None.

Additional context
Blocked by #2781.
Relates to #2780, #2781.
Part of #1021.

[nikolahoff]

@steffenkleinle for native high contrast mode is enabled in the device settings, right? So we would only need a toggle switch for web?
https://www.androidpolice.com/android-phone-enable-high-contrast-mode/

[steffenkleinle]

@steffenkleinle for native high contrast mode is enabled in the device settings, right? So we would only need a toggle switch for web? https://www.androidpolice.com/android-phone-enable-high-contrast-mode/

Sadly I can't find a way to get that information in the app :( So I think we still need a toggle on native... @LeandraH or @f1sh1918 can you think of another solution?

[LeandraH]

I don't find one either. There's a media query for it but that only works in web :(

[steffenkleinle]

@nikolahoff the setting is also just for high contrast text. I think we want more then that. Therefore I think we need a dedicate switch. Also this setting is only available on newer android versions. Something like the setting shown for samsung is even more device specific.