Apply suggestions from code review

Co-authored-by: Philip K.F. Hölzenspies <holzensp@gmail.com>

Author: HT154

pkl-core/src/main/java/org/pkl/core/util/yaml/ParseException.java

@@ -1,4 +1,4 @@
-/**
+/*
  * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");

pkl-core/src/main/resources/org/pkl/core/errorMessages.properties

@@ -797,9 +797,9 @@ jsonParseError=\
 Error parsing JSON document.
 
 jsonParseErrorDynamicPropertyDefault=\
-Cannot parse object with key `default` into ` Dynamic`.\
+Cannot parse an object with key `"default"` into a `Dynamic`.\
 \n\
-Try parsing into `Mapping` instead with `useMapping = true` in `pkl.json#Parser`.
+Try parsing into a `Mapping` instead, by setting `useMapping = true` in the `pkl.json#Parser`.
 
 yamlParseError=\
 Error parsing YAML document.
@@ -810,9 +810,9 @@ Error parsing YAML document: The number of aliases for collection nodes exceeds
 To increase the allowed maximum, set `YamlRenderer.maxCollectionAliases`.
 
 yamlParseErrorDynamicPropertyDefault=\
-Cannot parse object with key `default` into ` Dynamic`.\
+Cannot parse an object with key `default` into a `Dynamic`.\
 \n\
-Try parsing into `Mapping` instead with `useMapping = true` in `pkl.yaml#Parser`.
+Try parsing into a `Mapping` instead, by setting `useMapping = true` in the `pkl.yaml#Parser`.
 
 evaluationTimedOut=\
 Evaluation timed out after {0,number,#.##} second(s).