.gitignore everything under .vs in repo root dir

We have external users editing queries with Visual Studio, and it seems
to automatically add very specific files to `.gitignore`. These changes
cause conflicts between unrelated PRs.

This commit adds all of `/.vs` to `.gitignore`, which should hopfully
make Visual Studio stop adding more entries.

Author: jbj

.gitignore

@@ -1,5 +1,6 @@
 # editor and OS artifacts
 *~
+/.vs
 .DS_STORE
 
 # query compilation caches
@@ -8,8 +9,3 @@
 # qltest projects and artifacts
 */ql/test/**/*.testproj
 */ql/test/**/*.actual
-/.vs/slnx.sqlite
-/.vs/ql/v15/Browse.VC.opendb
-/.vs/ql/v15/Browse.VC.db
-/.vs/ProjectSettings.json
-