Added extensions.json as exception in .vscode folder. File is used as
extensions recommendation for project.

Visual Studio Code has a few files that can be placed into the workspace
in order to share settings across users.  Settings.json is for project
specific overrides.  Tasks.json is for executable tasks (build, gulp, etc.)
While launch.json is for debugging specific tasks.

Starting with 0.8.0, VS Code will store its settings in a .vscode folder and no longer in the generic .settings folder.