Pigframe

What's Changed
* Feature/component existance by passive-radio in https://github.com/passive-radio/pigframe/pull/6
* Feature/entity id convenience by passive-radio in https://github.com/passive-radio/pigframe/pull/7


**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.2.0...v0.2.1

**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.1.2...v0.2.0

What's new
- update README and README in Japanese
- world class can check the existance of components using `component_exist()` method.

What's Changed
* Feature/component existance by passive-radio in https://github.com/passive-radio/pigframe/pull/6


**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.1.1...v0.1.2

**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.1...v0.1.1

New features
- a new pyxel example project: simple top-down shooting game

Updates
- World class not does not omit error but None if enity doesn't exists when get_entity_object, remove_entity
- type hint to World methods

What's Changed
* Feateure/new pyxel example by passive-radio in https://github.com/passive-radio/pigframe/pull/5


**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.0.9.2...v0.1

**Full Changelog**: https://github.com/passive-radio/pigframe/compare/v0.0.9.1...v0.0.9.2