getSymbolAssetPath function
Provides the path to the PNG file located in the consumer app's assets.
By default, this generates paths in the format:
assets/icons/symbols/{assetCode}.png
Consumers can override this by providing a custom assetPathBuilder to
SymbolIcon.
Implementation
String getSymbolAssetPath(String assetCode) =>
'assets/icons/symbols/${assetCode.toLowerCase()}.png';