feat: export PackageJsonObject

[UrielCh]

Hi,

I'm writing a lot of dnt scripts currently, and I want them to be supper clean.

Right now my common don't script starts like this:

// dnt deps can not be moved to dev_deps.ts
import { build, emptyDir } from "https://deno.land/x/dnt@0.35.0/mod.ts";
import * as pc from "https://deno.land/std@0.188.0/fmt/colors.ts";
import { PackageJsonObject } from "https://deno.land/x/dnt@0.35.0/lib/types.ts";

and later I write my dnt build call like that:

const packageJson: PackageJsonObject = {
  name: "....",
  author: "...",
  license: "...",
  contributors: [
    "..."
  ],
  description: "...",
  keywords: [
    "...",
    "...",
  ],
  private: false,
  homepage: "...",
  version,
  /// ...
};
await emptyDir("./npm");
await build({
  entryPoints: ["./mod.ts"],
  outDir: "./npm",
  shims: {
    deno: true,
  },
  compilerOptions: {},
  package: packageJson,
});

For a clean code, I need to explicitly use type PackageJsonObject

with that change, the top of ma build script can be written:

// dnt deps can not be moved to dev_deps.ts
import { build, emptyDir, PackageJsonObject  } from "https://deno.land/x/dnt@0.35.0/mod.ts";
import * as pc from "https://deno.land/std@0.188.0/fmt/colors.ts";

that cleaner, and avoid repetition of dnt@0.35.0

I think I can be categorized as a "never nester"

I will put my ultimate dnt_build script in the doc at the end.

[dsherret]

LGTM

[dsherret]

I'm going to rename this as PackageJson in a future PR. The Object seems unnecessary.