Remove support for node 12 and ensure support for node 18

[bidoubiwa]

Node version compatibilities should be changed in the tests and the readme.

See related issue.

Previous ensured compatibilities:

• Node 12
• Node 13
• Node 14

New compatibilities to ensure:

• Node 14
• Node 16
• Node 18

TODO:

• [ ] Update requirements/compatibilities in README.md.
• [ ] Update node versions tested in CI tests.