[@rushstack/node-core-library] use the JsonFile.save() update existing json5 syntax file error.

[fansenze]

Summary

use the JsonFile.save(@rushstack/node-core-library) update existing json5 syntax file error.

Repro steps

• open this link

• execute node test.js in terminal

Actual result: it will cause error in terminal: SyntaxError: Trailing comma in object at 4:1

Expected result: save successfully.

Details

Currently:

• JsonFile.load set json5 mode to jju by default, so that can load files both json / cjson / json5 syntax.
• JsonFile.save not support json5 syntax string by default when set updateExistingFile as true.

Expected:
i think the default json syntax should remain consistent in JsonFile read/write functions.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
Package name:	@rushstack/node-core-library
Package version?	3.62.0
Operating system?	Mac
Would you consider contributing a PR?	No
Node.js version (node -v)?	16.16.0 / 20.10.0