FENCED_RULEconstant

Fenced code blocks

• Same as Markdown syntax.
• Start when we reach an opening fence on a new line.
• Stop when we reach a matching closing fence on a new line, or the end of the string.
• Closing fence must be exactly the same as the opening fence, and can be made of three or more "" backticks, or three or more ~~~` tildes.
• If there's no closing fence the code block will run to the end of the current string.
• Markdown-style four-space indent syntax is not supported (only fenced code since it's less confusing and more common).