Issue Type: <b>Feature Request</b> Currently when clicking or dragging on the completion details, it'll go away, making it impossible to select text inside it. VS Code version: Code - Insiders 1.26.0-insider (4fa62b246c4305b4ca00507551f77c58135ce928, 2018-08-03T12:25:19.888Z) OS version: Darwin x64 17.7.0  <!-- generated by issue reporter -->