add Markdown explanation to RFc

rfc/src/rfcs/0013-list.md

@@ -297,6 +297,12 @@ However, it also allows the compiler to take advantage of the build cache.
 If a user verifies their code and then invokes `list` (or vice versa),
 the compiler will be invoked with the same arguments both times, which means that it can just use the cached targets from the first compiler invocation.
 
+### Pretty Format
+The Contracts table is close to Markdown, but not quite Markdown--it includes line separators between each row,
+when Markdown would only have a separator for the header.
+We include the separator because without it, it can be difficult to tell from reading the terminal output which entries are in the same row.
+The user can transform the table to Markdown by deleting these separators, and we can trivially add a Markdown option in the future if there is demand.
+
 ## Open questions
 
 1. Do we want to include more contracts information? We could print more granular information about contracts, e.g., the text of the contracts or the number of `requires` and `ensures` contracts.