feat: allow customizing Vitest environment (#2149)

## PR Checklist

- [x] Addresses an existing open issue: fixes #2146
- [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

🎁

Author: JoshuaKGoldberg

src/blocks/blockVitest.test.ts

@@ -521,6 +521,7 @@ describe("blockVitest", () => {
 					exclude: ["other"],
 					include: ["src/"],
 				},
+				environment: "happy-dom",
 				exclude: ["lib/"],
 				flags: ["--typecheck"],
 			},
@@ -750,6 +751,7 @@ describe("blockVitest", () => {
 						include: ["src/"],
 						reporter: ["html", "lcov"],
 					},
+					environment: "happy-dom",
 					exclude: ["lib/","node_modules"],
 					setupFiles: ["console-fail-test/setup"],
 				},

src/blocks/blockVitest.ts

@@ -46,6 +46,7 @@ export const blockVitest = base.createBlock({
 	addons: {
 		actionSteps: z.array(zActionStep).default([]),
 		coverage: zCoverage.default({}),
+		environment: z.string().optional(),
 		exclude: zExclude.default([]),
 		flags: z.array(z.string()).default([]),
 	},
@@ -77,7 +78,7 @@ export const blockVitest = base.createBlock({
 		};
 	},
 	produce({ addons }) {
-		const { actionSteps, coverage, exclude = [] } = addons;
+		const { actionSteps, coverage, environment, exclude = [] } = addons;
 		const excludeText = JSON.stringify(
 			Array.from(new Set(["node_modules", ...exclude])).sort(),
 		);
@@ -243,7 +244,12 @@ export default defineConfig({
 					: ""
 			}include: ${JSON.stringify(coverage.include)},
 			reporter: ["html", "lcov"],
-		},
+		},${
+			environment
+				? `
+		environment: "${environment}",`
+				: ""
+		}
 		exclude: [${excludeText.slice(1, excludeText.length - 1)}],
 		setupFiles: ["console-fail-test/setup"],
 	},