Allow entering comma instead of point for decimal separator

With some keyboards (for example Swiftkey, see https://fuelio.userecho.com/en/communities/1/topics/50-please-add-numeric-keyboard-for-entering-fuel-data), it's not clear that we're supposed to use the dot (for non-US users).

It may actually have led to https://fuelio.userecho.com/en/communities/1/topics/147-no-decimal-fraction-edition-concerns
Even with the standard AOSP keyboard, the comma is shown.

Why not accept the comma and replace it internally by a dot (while still showing a comma as it already does)?