Add multi-line typing

[m229abd]

Hey there. So I realized OmniTool had problems with inserting multi-line text, I tried solving it by splitting the multi-line string and typing lines separately, but it caused problems with auto-indentation in VSCode. Then I tried using copy and paste and it works pretty well. Turns out this is also the method UI-TARS uses, even though I didn't know that at that moment. I also used base64 to make sure VLM outputs are transferred and pasted exactly. The code is tested.