Added types to the .gitignore (#3322)

We're using `types` in KeyVault's packages. We should ignore them.
Also, we're moving every package to have the types in this `types` folder. See: https://github.com/Azure/azure-sdk-for-js/pull/3329

.gitignore

@@ -138,6 +138,7 @@ browser
 test-browser
 typings
 typedoc
+types
 
 # autorest generated files
 swagger/*.json