Add vscode to .gitignore

Signed-off-by: Eunchan Kim <eunchan@opentitan.org>
diff --git a/.gitignore b/.gitignore
index ca354e0..c27565e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 *.bak
 tags
 __pycache__
+/.vscode
 opentitan-docs
 
 # fusesoc result