Add linting

[lukekarrys]

This goes on top of #18. Keeping in draft until that lands.

Lint only diff: 5409823

This is ready for review.

[lukekarrys]

This was a bug found via linting:

import { jack } from "jackspeak";
const j = jack()
  .opt({
    x: {
      description: "desc",
    },
  })
  .opt({
    x: {
      description: "desc",
    },
  });

file:///Users/lukekarrys/Desktop/scratch/jackspeak-lint-changes/node_modules/jackspeak/dist/esm/index.js:571
            throw new TypeError(`Cannot redefine option ${field}`);
                  ^

TypeError: Cannot redefine option [object Object]

[lukekarrys]

This was also found via linting. The change helps distinguish between primitive and non-primitive values in error messages:

import { jack } from "jackspeak";

const j = jack()
  .optList({ xlist: { validate: () => false } })
  .opt({ x: { validate: () => false } });

const validate = (o) => {
  try {
    j.validate(o);
  } catch (e) {
    console.log(e.message);
  }
};

validate({ xlist: ["a", "b", "c"] });
validate({ x: "a,b,c" });

before

❯ node index.mjs
Invalid config value for xlist: a,b,c
Invalid config value for x: a,b,c

after

❯ node index.mjs
Invalid config value for xlist: ["a","b","c"]
Invalid config value for x: "a,b,c"