fix: include bin entry in package.json files (#1149)

## PR Checklist

- [x] Addresses an existing open issue: fixes #1147
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Includes a `files` entry if `bin` exists. Also strips a preceding `./`
from it if it's there.

Author: JoshuaKGoldberg

package.json

@@ -15,7 +15,7 @@
 	"main": "./lib/index.js",
 	"bin": "./bin/index.js",
 	"files": [
-		"bin/",
+		"bin/index.js",
 		"lib/",
 		"package.json",
 		"LICENSE.md",

script/__snapshots__/migrate-test-e2e.js.snap

@@ -273,14 +273,6 @@ exports[`expected file changes > knip.jsonc 1`] = `
 exports[`expected file changes > package.json 1`] = `
 "--- a/package.json
 +++ b/package.json
-@@ ... @@
- 	"main": "./lib/index.js",
- 	"bin": "./bin/index.js",
- 	"files": [
--		"bin/",
- 		"lib/",
- 		"package.json",
- 		"LICENSE.md",
 @@ ... @@
  	"scripts": {
  		"build": "tsup",

src/steps/writing/creation/writePackageJson.test.ts

@@ -124,6 +124,7 @@ describe("writePackageJson", () => {
 
 		const packageJson = await writePackageJson({
 			...options,
+			bin: "./bin/index.js",
 			excludeAllContributors: true,
 			excludeCompliance: true,
 			excludeLintJson: true,
@@ -144,12 +145,14 @@ describe("writePackageJson", () => {
 			    "email": "[email protected]",
 			    "name": "test-author",
 			  },
+			  "bin": "./bin/index.js",
 			  "description": "Test description.",
 			  "devDependencies": {},
 			  "engines": {
 			    "node": ">=18",
 			  },
 			  "files": [
+			    "bin/index.js",
 			    "lib/",
 			    "package.json",
 			    "LICENSE.md",

src/steps/writing/creation/writePackageJson.ts

@@ -60,7 +60,13 @@ export async function writePackageJson(options: Options) {
 		engines: {
 			node: ">=18",
 		},
-		files: ["lib/", "package.json", "LICENSE.md", "README.md"],
+		files: [
+			options.bin?.replace(/^\.\//, ""),
+			"lib/",
+			"package.json",
+			"LICENSE.md",
+			"README.md",
+		].filter(Boolean),
 		license: "MIT",
 		"lint-staged": {
 			"*": "prettier --ignore-unknown --write",