New API:

```kotlin
fun TypefaceFontProvider.createAsFallbackProvider(): TypefaceFontProvider
fun FontMgr.defaultWithFallbackFontProvider(fallback: TypefaceFontProvider): FontMgr
```

Usage:

```kotlin
val fontCollection = FontCollection()

val notoEmojiTypeface = Typeface.makeFromData(Data.makeFromBytes(notoEmojisBytes))
val fallbackProvider = TypefaceFontProvider.createAsFallbackProvider().apply {
    registerTypeface(notoEmojiTypeface)
}

fontCollection.setDefaultFontManager(FontMgr.defaultWithFallbackFontProvider(fallbackProvider))
```

<img width="400" alt="Screenshot 2024-06-07 at 14 48 28"
src="https://github.com/JetBrains/skiko/assets/7372778/76dc1330-d8e2-4be7-ad92-68214b058b4f">