chore: Build with tsup to ensure consistent types

[TrevorBurnham]

This commit switches to tsup to build from TypeScript instead of using tsc directly, and defines additional entrypoints in package.json.

This fixes some complaints about the built types that arethetypeswrong reported, ensuring compatibility with all consumers.

Before

$ npx --yes @arethetypeswrong/cli --pack .

🤨 CommonJS module simulates a default export with exports.default and exports.__esModule, but does not also set module.exports for compatibility with Node. Node, and some bundlers under certain conditions (https://andrewbranch.github.io/interop-test/#synthesizing-default-exports-for-cjs-modules), do not respect the __esModule marker, so accessing the intended default export will require a .default property access on the default import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSOnlyExportsDefault.md

┌───────────────────┬───────────────────────┬──────────────────────┬─────────────────────────────────┐
│                   │ "next-router-mock"    │ "next-router-mock/*" │ "next-router-mock/package.json" │
├───────────────────┼───────────────────────┼──────────────────────┼─────────────────────────────────┤
│ node10            │ 🟢                    │ (wildcard)           │ 🟢 (JSON)                       │
├───────────────────┼───────────────────────┼──────────────────────┼─────────────────────────────────┤
│ node16 (from CJS) │ 🟢 (CJS)              │ (wildcard)           │ 🟢 (JSON)                       │
├───────────────────┼───────────────────────┼──────────────────────┼─────────────────────────────────┤
│ node16 (from ESM) │ 🤨 CJS default export │ (wildcard)           │ 🟢 (JSON)                       │
├───────────────────┼───────────────────────┼──────────────────────┼─────────────────────────────────┤
│ bundler           │ 🤨 CJS default export │ (wildcard)           │ 🟢 (JSON)                       │
└───────────────────┴───────────────────────┴──────────────────────┴─────────────────────────────────┘

After

$ npx --yes @arethetypeswrong/cli --pack .

 No problems found 🌟

"next-router-mock"

node10: 🟢 
node16 (from CJS): 🟢 (CJS)
node16 (from ESM): 🟢 (CJS)
bundler: 🟢 

"next-router-mock/*"

node10: (wildcard)
node16 (from CJS): (wildcard)
node16 (from ESM): (wildcard)
bundler: (wildcard)

"next-router-mock/package.json"

node10: 🟢 (JSON)
node16 (from CJS): 🟢 (JSON)
node16 (from ESM): 🟢 (JSON)
bundler: 🟢 (JSON)

[changeset-bot]

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Latest commit: cfe449c

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