feat!: remove node 12 and node 14

[lholmquist]

Node 12 has been EOL since the end of April 2022 and Node 14 just became EOL at the end of April 2023

This is a major version bump

[lholmquist]

@lance ^^

[lance]

@lholmquist it looks like the error message thrown with JSON parsing changed in v20. Can you also modify the expectation on line 59 of test/integration/parser_test.ts and remove the text validation?

    expect(parser.parse.bind(parser, payload)).to.throw(SyntaxError);

[lholmquist]

@lance updated and looks like it passes now.

Hopefully this also generates a release pr 🤞