lint: add tsconfig for browser_tests, fix existing violations (#5633)

## Summary

See https://typescript-eslint.io/blog/project-service/ for context.
Creates a browser_tests specific tsconfig so that they can be linted.

Does not add a package.json script to do the linting yet, but `pnpm exec
eslint browser_tests` should work for now.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5633-lint-add-tsconfig-for-browser_tests-fix-existing-violations-2726d73d3650819d8ef2c4b0abc31e14)
by [Unito](https://www.unito.io)

tests-ui/tests/renderer/extensions/vueNodes/composables/useNodeEventHandlers.test.ts

@@ -2,7 +2,7 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { ref } from 'vue'
 
 import type { VueNodeData } from '@/composables/graph/useGraphNodeManager'
-import { useGraphNodeManager } from '@/composables/graph/useGraphNodeManager'
+import type { useGraphNodeManager } from '@/composables/graph/useGraphNodeManager'
 import type { LGraphCanvas, LGraphNode } from '@/lib/litegraph/src/litegraph'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { useLayoutMutations } from '@/renderer/core/layout/operations/layoutMutations'

tests-ui/tests/renderer/extensions/vueNodes/widgets/composables/useRemoteWidget.test.ts

@@ -2,7 +2,7 @@ import axios from 'axios'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { useRemoteWidget } from '@/renderer/extensions/vueNodes/widgets/composables/useRemoteWidget'
-import { RemoteWidgetConfig } from '@/schemas/nodeDefSchema'
+import type { RemoteWidgetConfig } from '@/schemas/nodeDefSchema'
 
 vi.mock('axios', () => {
   return {