feat: @deno-types map in build options

[nayeemrmn]

Adds support for a deno.json field like:

{
  "types": {
    "npm:express": "npm:@types/express",
    "./file.js": "./file.d.ts"
  }
}

All specifiers written there are resolved through provided resolver with the deno.json as the referrer. So an import-mapped key (or value) will just work:

{
  "imports": {
    "express": "npm:express@^4.18.3"
  },
  "types": {
    "express": "npm:@types/express@^4.17.21"
  }
}

We can make it so that deno add npm:@types/<package> adds the entry to "types" instead of "imports". So deno add npm:@types/express will be the equivalent of npm i --save @types/express.

These mappings will only apply to referrers within the passed 'scope' associated with the deno.json. In CLI we would presumably pass the parent directory of the deno.json file.

JSR will inline these mappings to pragmas on publish. This has parity with the above behaviour.

---

This is essentially // @deno-types pragmas in config file form. Reasons we want to do this:

• Deduplicate // @deno-types pragmas for dependencies.
• Pragmas can't be used for things like compilerOptions.jsxImportSource.
• NPM @types packages can be referenced and version-pinned in the config file next to their runtime counterparts.

[marvinhagemeister]

I quite like this idea. Makes a lot of sense to put it in the config file for imports defined there 👍