tools: add .vscode folder to .gitignore

PR-URL: https://github.com/nodejs/node/pull/7967
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jackson Tian <shvyo1987@gmail.com>

.gitignore

@@ -42,6 +42,7 @@ ipch/
 *.opensdf
 *.VC.opendb
 .vs/
+.vscode/
 
 /config.mk
 /config.gypi