Feature request: TableOfContents optionally on left side

For me the table of contents is a bit in the way, because I quite like the Live docs. They overlap and it also just feels cluttered.

I would love an option where I can go TableOfContents(side=:left) and then the floating TOC shows up on the left side.

Would do it myself, but I have no clue when it comes to JavaScript.

Love PlutoUI, thanks for all the hard work!