…fig.ts

Hoist eslint from packages/vfm to the workspace root to share a single
lint configuration across both vfm and remark-attribute.

- Replace eslint@8, @typescript-eslint/eslint-plugin@5, and
  @typescript-eslint/parser@5 with eslint@10, @eslint/js, and
  typescript-eslint@8.
- eslint@10 requires flat config (eslint.config.*), so migrate
  .eslintrc.js to the new format using defineConfig + globals.
- Adopt eslint.config.ts instead of .js. Native .ts config support in
  eslint still requires the unstable_native_nodejs_ts_config flag
  (see eslint/eslint#19985), but eslint falls back to jiti when it is
  installed. Since vfm already had jiti as a transitive dependency
  (via vitest and release-it), add it explicitly to the root
  devDependencies to make this intentional.

Hoist prettier from packages/vfm to the workspace root and upgrade
from v2 to v3. Migrate .prettierrc to prettier.config.ts.

Source file changes are reformatting by prettier v3.

Move typescript (^4.8.3 -> ^6.0.2) and @types/node (^18/^20 -> ^20)
from individual packages to the workspace root.

Add "types": ["node"] to packages/vfm/tsconfig.json, required by
TypeScript 6 which no longer auto-includes @types/node.