Tracks picking up TypeScript 3.1. We plan to ship this as the bundled typescript version with the September release of VS Code

Relevant tooling work:

• Cannot fold js/ts file header before 'use strict' #50899 - Folding js/ts header before use strict
• Support triggering rename on import path in js/ts #51175 - Trigger rename on import path
• [TypeScript] Cancel geterr before any user-invoked operation #57542 Cancel geterr
• Add context information to SignatureHelpProvider #54972 Completion context