Add a table of markdown -> manuscript conversions

[AdamIsrael]

Make a table to document the Markdown characters that get converted to something else in the compiled manuscript.

For example,

Markdown	Manuscript	Reasoning
---	Centered #	Traditional scene breaks are hard to replicate in Markdown. Use a horizontal breaks between scenes in a single Markdown document and convert them to a centered #

There’s probably more examples of conversions (now or in the future) so get them documented now.