core: Add show for ParserError

src/Parser/Interface.md

@@ -25,6 +25,16 @@ record ParseError where
   message : String
 ```
 
+<!-- idris
+export
+Show ParseError where
+  show (MkParseError state message) = 
+    let (line, col) = positionPair state
+        (line, col) = (show line, show col)
+        position = show state.position.index
+    in "Error at line \{line}, column \{col} (\{position}): \{message}"
+-->
+
 ## Type Alias
 
 ```idris