use satisfies instead of direct type for JSONSchema

[cyrilletuzi]

TypeScript 4.9 introduced satisfies, which solves an old typing pain point for JSONSchema. Refer to the TypeScript documentation for an explanation.

Note it is just a documentation change, direct typing still works.

Below is an example from this library of the difference between direct typing and satisfies:

const schema1 = {
  type: "object",
  properties: {
    title: { type: "string" },
  },
  required: ["title"],
} satisfies JSONSchema;

schema1.properties.title; // OK!

const schema2: JSONSchema = {
  type: "object",
  properties: {
    title: { type: "string" },
  },
  required: ["title"],
};

schema2.properties.title; // Not OK
schema2.properties["title"]?.type; // OK, but type includes `undefined`

Note that there is still some type widening happening. The best solution would be:

const schema = {
  type: "object",
  properties: {
    title: { type: "string" },
  },
  required: ["title"],
} as const satisfies JSONSchema;

Thus the schema is kept fully intact, without any type widening, while still having autocomplete and type check.