chore: add .vscode/settings.json file (#6967)

This ensures that:

- The ESLint config file used by VSCode is always the correct one and
  that the working directory can always be identified. VSCode could
  become confused if this project is checked out inside a folder named
  `node_modules` and start complaining about unpublished files every
  place we reference a relative file in a `require` call.
- The TypeScript version used by VSCode is the same as being used by the
  project.

Author: watson

.vscode/settings.json

@@ -0,0 +1,9 @@
+{
+  "eslint.workingDirectories": [
+    "."
+  ],
+  "eslint.options": {
+    "overrideConfigFile": "${workspaceFolder}/eslint.config.mjs"
+  },
+  "typescript.tsdk": "node_modules/typescript/lib"
+}