[FEAT] Bump Typescript target to Node 14 (ES2020)

[Ginden]

This change:

• Improves performance (native async/await is faster than __awaiter)
• Improves debugging (error stacktraces are preserved through async/await)
• Reduces bundle size a bit (no var __awaiter in generated code)

This should be a safe change, as Node 14 is already required.