build: add .DS_store to .gitgnore

The following files were not being ignored:

deps/npm/node_modules/node-gyp/gyp/tools/.DS_Store
deps/npm/node_modules/node-gyp/gyp/tools/Xcode/.DS_Store

PR-URL: https://github.com/nodejs/node/pull/23554


Reviewed-By: Hitesh Kanwathirtha <digitalinfinity@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>