Upgrade to Node 18 LTS

We should upgrade from Node 12 to Node 16 LTS.

Here are some resources which will help with the upgrade to deal with breaking changes:

• https://nodejs.org/en/blog/release/v13.0.0/#semver-major-commits
• https://nodejs.org/en/blog/release/v14.0.0/#semver-major-commits
• https://nodejs.org/en/blog/release/v15.0.0/#semver-major-commits
• https://nodejs.org/en/blog/release/v16.0.0/#semver-major-commits

Relates to #329 (closed)