[TIDOC-1847] Added multi-level TOC to cloud guide pages.

Number of <hN> tags that are included in TOC is determined by `max_level` property (https://github.com/tstatler/jsduck/commit/10e16a229b78d96cc90944932e29a317e160a706#diff-17d206e88a0907b6f9cd241f8887fec8R13).