Advanced markdown tricks and tips

This section contains all those less known markdown tricks:

• very simple to use but somehow not widely known tricks like double-space to create a new line or triple dash for an hr
• neat visual features like nested lists and coloring code blocks according to the language syntax
• more complex things like reference links and tables

Remember - all these uses are not specific to MDTX and should work wherever markdown is used (eg. GitHub, Medium or Reddit)