Changelog for hierarchical-env-0.2.0.0

Revision history for hierarchical-env

0.2.0.0 -- 2021-04-28

Change how to specify the super environment
- Before: Specify by adding type instance for Super env
```
data Env = Env !BaseEnv !Int
deriveEnv ''Env
type instance Super Env = BaseEnv
```
- After: Wrapping the super environment field with Extends
```
data Env = Env !(Extends BaseEnv) !Int
deriveEnv ''Env
```
Fix the type error bug occurs when hiding dependencies.

0.1.0.0 -- 2021-04-22

First version. Released on an unsuspecting world.