added "📦 Download Subtitle" button | added ngrok support for public link | add more arguments in "⚙️Setting"

[ShuYuHuang]

1. The idea of creating ".srt" file is super powerful, but the file can't be downloaded directly, so I added a button.
2. Adding public link is only for my promotion events, just F.Y.I
3. I added some setting arguments for our use and change default language as "zh" because I'm targeting Chinese users, just F.Y.I.

I love the design of icons and layouts by the way~~