Excluding Table of Contents entry in TOC

[yisiliu]

Hi Hackmd team! Thanks for your hard work to provide us such a wonderful markdown collaboration platform. However, I am frustrated that Table of Contents entry is included in the actual Table of Contents by using [TOC] in both Hackmd and Codimd. I think a tentative solution to this is to explicitly exclude a few key words like Table of Contents and 目录 in [TOC] to make it clearer. An alternative solution might be supporting a special tag to be ignored by [TOC]. What do you guys think? The actual behavior is shown below: