[Feat] copy whole file if there is no selection

[givvemee]

Closes #38

Description

• This feature let YOCO copy the whole file if there's no selections.

ETC

• It's already passed the test, but @fliklab @glassk could you test on your end to validate this feature? Thank you in advance

Checklist (Merge should only be performed once all of the following conditions are checked.)

• I have completed the necessary tests and verified that the functionality works as intended.
• I have written the code according to the code style guide.
• I have confirmed that only the intended files and changes have been committed.
• I have discussed these changes with my team members in advance, and all team members are aware of this PR.

[glassk]

제 로컬 환경에서도 테스트 통과했습니다! 고생 많으셨습니다 👍