[Examples] All supported sources and their config examples

- LittleSkin
```toml
[LittleSkin]
type = "BLESSING_SKIN"
apiRoot = "https://littleskin.cn/api/yggdrasil/"
ordinal = 0
```
- ely.by
```toml
[ElyBy]
type = "BLESSING_SKIN"
apiRoot = "https://account.ely.by/api/authlib-injector/"
ordinal = 0
```