Update 0.3.0

Most of the work done on this release was invisible refactoring. But one important bug fix came up that I wanted to update the game for.

• Fixed a bug where e.g. 大丈夫 and だいじょうぶ could be active targets at the same time.
• Added a few new words to the kana list that use ワ.
• Removed an unnecessary bevy feature that was bringing in 3d features.
  This may have (positive) performance implications on the web.
• Major refactoring of asset loading code to use the excellent bevy_asset_loader
• Other minor code quality improvements