src/components: add get statistics data function in StatsBar component

[maceksimon]

Update StatsBar component to make it work with API data source:

• Add useStatsBar composable and define functions for getting icon, label and unit.
• Update StatsBar to use composable functions.
• Create a fixture based on actual API output and add types for it.
• Create a function that computes statistics array for display and use it on the wrapping components (for control over which kind of stats we want to show).
• Merge custom icons into a single file with component-based name.