Simple Word Book

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- Added a setting to sort wordbooks
- Added a setting to change text align in memorize screen
- Added a feature to mark words as your "weak point"
- Modified "edit word" screen to focus on "surface" text field
- Fixed "edit word" screen that window closes even when there is input errors
- Fixed "edit word" screen to show warnings on tapping left arrow icon or back key
- Modified "settings" screen to show current settings
- Modified UI design