Add ComponentType.Get(World, *donburi.Entry) Method

[Yota Hamada]

Add Generics method and eliminate the need for making tons of helper functions like this. Also, it will be Type-safe!

func GetVelocity(entry *donburi.Entry) *VelocityData {
  return donburi.Get[VelocityData](entry, Velocity)
}

• Add (c *ComponentType[T]) ComponentType.Get(World, *donburi.Entry) *T
• Add (c *ComponentType[T]) ComponentType.Set(World, *donburi.Entry, *T)
• Add (c *ComponentType[T]) ComponentType.SetValue(World, *donburi.Entry, T)
• Update README.md

[Yota Hamada]

Done in v1.3.0