ci: Explicitly add DOM types

CI for the `integration-test` project is currently failing with:

```console
Error: node_modules/@types/jsdom/base.d.ts(24,40): error TS2304: Cannot find name 'DocumentFragment'.
Error: node_modules/@types/jsdom/base.d.ts(41,28): error TS2304: Cannot find name 'Node'.
Error: node_modules/@types/jsdom/base.d.ts(172,19): error TS2304: Cannot find name 'HTMLScriptElement'.
Error: node_modules/@types/jsdom/base.d.ts(172,39): error TS2304: Cannot find name 'HTMLLinkElement'.
Error: node_modules/@types/jsdom/base.d.ts(172,57): error TS2304: Cannot find name 'HTMLIFrameElement'.
Error: node_modules/@types/jsdom/base.d.ts(172,77): error TS2304: Cannot find name 'HTMLImageElement'.
Error: node_modules/@types/jsdom/base.d.ts(181,38): error TS2304: Cannot find name 'Window'.
Error: node_modules/@types/jsdom/base.d.ts(185,24): error TS2304: Cannot find name 'Window'.
```

This suggests TypeScript cannot find types definitions for JsDOM. JsDom is a transitive dependency via Jest.

In this change we explicitly add the DOM types to tsconfig to solve this.

I don't fully understand why this has suddenly started happening.
I suspect our lack of a lockfile on the `integration-test` project might have something to do with it.

I also don't fully understand why we didn't see CI issues in #931 which bumped the version of TypeScript...

See: https://www.typescriptlang.org/tsconfig#high-level-libraries

tools/integration-test/tsconfig.json

@@ -8,7 +8,7 @@
     "target": "ES2020",
     "module": "ES2020",
     "moduleResolution": "node",
-    "lib": ["ES2020"],
+    "lib": ["ES2020", "DOM"],
     "declaration": true,
     "strict": true,
     "noImplicitAny": true,