Update sign-up-for-talks.md

[Tzyinc]

Introduction: Ten is a fe dev in the web team, who sometimes reads textbooks when he has no features to work on. In this talk, we will cover some interesting examples from the series of text books "You don't know javascript" and figure out why the javascript engine acts differently from how we might expect it to

[wgao19]

Hi @Tzyinc , could you please include a brief introduction to your talk (in the description of this MR is fine, no need code change). Also provide a introduction to yourself to be used by MC to introduce you before your talk :] Thanks.

[Tzyinc]

updated