chore(Node.js): Add Node.js 12 to CI
chore(Node.js): Add Node.js 12 to CI

Node.js 12 (and especially Node.js 12.9) is supposed to be significantly
faster than previous versions, especially when it comes to parsing JSON, which
is often a bottleneck for Pelias importers.

https://nodejs.org/en/blog/release/v12.9.0/
https://v8.dev/blog/v8-release-76

Connects https://github.com/pelias/pelias/issues/800

pelias/openstreetmap,pelias/openstreetmap