Add the content sidebar of a singe markdown file to the website

Now the IoTDB [website](https://iotdb.apache.org/UserGuide/Master/QuickStart/QuickStart.html) has the left sidebar to guide through different markdown files,
but lacks the right sidebar to guide through the different sections in a single markdown file.
It's easy to get lost when reading a long markdown without a content sidebar.

No source file, test, or entry point is named. Start by inspecting the linked IoTDB website and locating how its Markdown pages are generated; confirm how section headings are represented. Done means long single-page Markdown documents display a right-hand content sidebar linking to their sections.

Written by the indexing model from the issue text.