Don't consume implicit newline delimiters.

Newlines should act as implicit delimiters for more than one nested set
in the absence of explicit delimiters.
For instance in "A:B:C\nD" the newline makes D a sibling of A.

source/md_impl.c

@@ -1700,7 +1700,7 @@ _MD_ParseSet(MD_ParseCtx *ctx, MD_Node *parent, _MD_ParseSetFlags flags,
                     child->flags |= MD_NodeFlag_BeforeSemicolon;
                     next_child_flags |= MD_NodeFlag_AfterSemicolon;
                 }
-                result |= !!MD_Parse_Require(ctx, MD_S8Lit("\n"), MD_TokenKind_Newline);
+                result |= (MD_Parse_PeekSkipSome(ctx, 0).kind == MD_TokenKind_Newline);
                 if(result && terminate_with_separator)
                 {
                     goto end_parse;