TOC without scrolling and without boundary area

Greetings!

HackMD is great! Thank you. It doesn't have many glitches. Is sharp and precise!

One thing makes me feel uncomfortable - especially when I present things to the audience, or working together over a text:

**Is your feature request related to a problem? Please describe.**
In my opinion TOC is cramped when being inside specific area with scroll bar. Behavior is a little messy and visibility of expanded TOC is decreased. This includes additional scroll bar which looks not proffesional.

**Describe the solution you'd like**
Free the TOC - remove boundary area. Remove scroll bar when TOC is expanded. Put marking at top or bottom if TOC exceeds the screen.

It is not a feature not a bug. Just UX enchancement and (subjective) quality improvement.