Add skia.conf (configuration file that supports printShaders, etc...) to .gitignore

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1734563003

Review URL: https://codereview.chromium.org/1734563003
1 file changed