refactor [NET-1644]: Clean-up tsconfigs for the browser-test-runner package (#3268)

This pull request updates the TypeScript build and lint configuration
for the `browser-test-runner` package to use the main `tsconfig.json`
instead of `tsconfig.node.json`. It also adds a new script for
type-checking without emitting output.

### Changes

**Build and TypeScript configuration updates:**

* Changed the ESLint TypeScript parser configuration in
`eslint.config.mjs` to use `tsconfig.json` instead of
`tsconfig.node.json` for project references.
* Updated the `build` script in `package.json` to use the default
`tsconfig.json` and added a `check` script for running TypeScript type
checks without emitting files.

Author: mondoreale

packages/browser-test-runner/eslint.config.mjs

@@ -17,7 +17,7 @@ export default [
                     process: 'readonly'
                 },
                 parserOptions: {
-                    project: ['./tsconfig.node.json'],
+                    project: ['./tsconfig.json'],
                     tsconfigRootDir: __dirname
                 }
             }

packages/browser-test-runner/package.json

@@ -13,7 +13,8 @@
     "./dist/src/exports.js": false
   },
   "scripts": {
-    "build": "tsc -b tsconfig.node.json",
+    "build": "tsc -b",
+    "check": "tsc --noEmit",
     "eslint": "eslint --cache --cache-location=node_modules/.cache/.eslintcache/ '**/*.{js,ts}'"
   },
   "author": "Streamr Network AG <[email protected]>",