Update src/backend/parser/README

New files have been added to this directory, but not listed here.
Repair.

src/backend/parser/README

@@ -18,7 +18,10 @@ parse_coerce.c	handle coercing expressions to different data types
 parse_collate.c	assign collation information in completed expressions
 parse_cte.c	handle Common Table Expressions (WITH clauses)
 parse_expr.c	handle expressions like col, col + 3, x = 3 or x = 4
+parse_enr.c	handle ephemeral named rels (trigger transition tables, ...)
 parse_func.c	handle functions, table.column and column identifiers
+parse_jsontable.c handle JSON_TABLE
+parse_merge.c	handle MERGE
 parse_node.c	create nodes for various structures
 parse_oper.c	handle operators in expressions
 parse_param.c	handle Params (for the cases used in the core backend)