[docs] add more demo gifs for readme.md

[fliklab]

Description

• Add more gifs and embed into readme.md
• Replace main gif(the first one) into full-window shot

ETC

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.

[givvemee]

간단하게 description 이라도 채워주심이 어떨까여. "제곧내" 도 괜찮습니다 ^^

[fliklab]

간단하게 description 이라도 채워주심이 어떨까여. "제곧내" 도 괜찮습니다 ^^

PR을 먼저 올리고 내용을 수정하는편인데 PR이 올라가면서 바로 리뷰 리퀘스트 되어서 빈 내용으로 리뷰를 받게 되는 경우가 종종 있는것 같네요

[glassk]

깔끔한 이미지 감사합니다!