fix: removes the object when editing hex inputs of the color picker. (fix #504)

[lja1018]

Please check if the PR fulfills these requirements

• It's submitted to right branch according to our branching model
• It's right issue type on title
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• It does not introduce a breaking change or has description for the breaking change

Description

Fixed a bug that removed the object when editing the hex input of the color picker.

• AS-IS

  • 

• TO-BE

  • Object is not removed, only the input box is modified.

• Solution

  • For each input box of submenus, add focus and blur event handler to generate inputBoxEditingStarted and inputBoxEditingStoped events to determine whether the color(hex) value is being edited or not.
  • The events in the submenu are received by the ui and re-fire, and the events are received in the imageEditor to know if the input box of the color picker is being editted.

---

Thank you for your contribution to TOAST UI product. 🎉 😘 ✨

[heenakwag]

리뷰 완료합니다.