chore: dropping node 14 support

[nicholasgriffintn]

Resolves #362

Description:

This PR removes support for Node v14 due to the removal of security support from April 30th, 2023

Type of change:

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Why is this change required?:

To support new functionality, such as the AbortController, we would need a polyfill to continue to support this version.

Alongside this, if the version is not supported by the Node.JS team, we cannot confidently support Node 14 for our users without further work.

Code changes:

• Changed the coverage CI to run from the LTS
• Remove v14 from the test CI matrix
• Added a note to the README to make it clear that we no longer support this version of Node
• Added a minimum engine version to the package.json so that this is clear (16.19.0)

---

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codeclimate[bot]]

Code Climate has analyzed commit 47f3e9f4 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (80% is the threshold).

This pull request will bring the total coverage in the repository to 94.3% (0.0% change).

View more on Code Climate.