added .DS_Store file to .gitignore (#950)
added .DS_Store file to .gitignore (#950)

* added .DS_Store file to .gitignore

https://en.wikipedia.org/wiki/.DS_Store

* added missing new line to .gitignore

linsun/istio.github.io,istio/istio.io,linsun/istio.github.io,linsun/istio.github.io,istio/istio.io,ZackButcher/istio.github.io,geeknoid/istio.github.io,geeknoid/istio.github.io,linsun/istio.github.io,jasminejaksic/istio.github.io,jasminejaksic/istio.github.io,ZackButcher/istio.github.io,istio/istio.io,jasminejaksic/istio.github.io,linsun/istio.github.io,istio/istio.io,geeknoid/istio.github.io,ZackButcher/istio.github.io,ZackButcher/istio.github.io,istio/istio.io,istio/istio.io,geeknoid/istio.github.io,geeknoid/istio.github.io,jasminejaksic/istio.github.io,istio/istio.io