Upgrade to node14 and uWebsockets17.6

[tiffanyhan]

Issue - Enhancement

Node 13 does not have full support for the package.exports feature, and is not a Node LTS version. We should upgrade to Node14, the latest current stable version. Our current version of uWebSockets, 17.3.0 is not compatible with Node14. But uWebSockets 17.6.0 is. uWebSockets 18 is out but it's a breaking change. We should upgrade both of these packages together.

Major Node.js versions enter Current release status for six months, which gives library authors time to add support for them. After six months, odd-numbered releases (9, 11, etc.) become unsupported, and even-numbered releases (10, 12, etc.) move to Active LTS status and are ready for general use. LTS release status is "long-term support", which typically guarantees that critical bugs will be fixed for a total of 30 months. Production applications should only use Active LTS or Maintenance LTS releases.

Acceptance Criteria

• project can run locally for development purposes with upgraded dependencies

• project can build and pass CI with upgraded dependencies

• production behavior should stay the same, as verified via Release Tests in the next release

• Estimated effort: 4 hours (see CONTRIBUTING.md)