Update theme packages

[eebbi]

Project: Tampereen kaupunki, konsernihallinto / Tietohallintoyksikkö:
Project task: Tampere multisite support

Task: https://hiondigital.atlassian.net/browse/TMS-1025
Task title: Projektin ylläpito

[Copilot]

Pull request overview

Updates the theme build/tooling stack (Node + webpack ecosystem) to support newer dependency versions as part of ongoing maintenance for Tampere multisite support.

Changes:

• Migrate webpack config toward Webpack 5 conventions (asset modules, resolve.fallback, ESLint via eslint-webpack-plugin).
• Bump Node version and update a wide set of frontend build/lint dependencies.
• Update CI workflow Node setup, plus a small JS runtime bugfix in Toggle.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
webpack.config.js	Updates webpack config for Webpack 5 (asset modules, ESLint plugin, resolve.fallback).
package.json	Upgrades build/lint toolchain dependencies (webpack 5, loaders, ESLint, etc.).
CHANGELOG.MD	Notes the Node/webpack/dependency version updates in Unreleased.
assets/scripts/toggle.js	Fixes typeof comparison when reading optional duration data attribute.
.nvmrc	Pins Node to v18.20.4.
.github/workflows/phpcs-check.yml	Updates actions/cache to v4.
.github/workflows/npm-check.yml	Updates setup-node to v4 and moves CI Node to 18.x.

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