test: update .gitignore with .DS_Store for macOS

[tommyZZM]

Checklist

• commit message follows commit guidelines

Affected core subsystem(s)

no

fix flowing not Untracked files message on git status

node-chakracore$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Untracked files:
  (use "git add <file>..." to include in what will be committed

        .DS_Store
	chakrashim/.DS_Store
	npm/.DS_Store
	openssl/.DS_Store
	openssl/openssl/.DS_Store
	v8/.DS_Store
	v8/test/.DS_Store
	v8/test/mjsunit/.DS_Store
	../tools/eslint/.DS_Store
	../tools/eslint/node_modules/.DS_Store

[kfarnung]

@tommyZZM Thanks for your contribution! I'm wondering if this is something that would be good to do upstream in nodejs/node and then it will merge into here.

/cc @kunalspathak

[kunalspathak]

I agree with @kfarnung . This should be made in upstream first.

[kfarnung]

Created an upstream PR using @tommyZZM change.

nodejs/node#14721

[kfarnung]

@tommyZZM, please continue the discussion over at nodejs/node#14721.