Add adaptive app icon

[sethidden]

Hello,

I noticed the app does not have an adaptive icon for when you enable themed icons within Android. This is of course not a big deal as it's only a visual thing.

Icon suggestions

I can see that the logo is the Greek 2 euro coin, which may prove difficult to find a SVG for.
Here are some alternatives from Wikimedia:

• https://commons.wikimedia.org/wiki/File:Coin-155597.svg
• https://commons.wikimedia.org/wiki/File:2_Euro_Coin_-_Simple_Worksheet_Design.svg
• https://commons.wikimedia.org/wiki/File:1_Euro_Coin_-_Simple_Worksheet_Design.svg

The icons are public domain.

Docs

For more info about adaptive icons, see https://developer.android.com/develop/ui/views/launch/icon_design_adaptive

Screenshot