Update dependencies

[ltrung]

Description of changes: Update various dependencies for the demo:

• Migrating to webpack 5.
• Migrating to css-loader 5.
• Update postcss and ssri to newer version.
• Swap typed-css-modules-webpack-plugin for typings-for-css-modules-loader because typed-css-modules-webpack-plugin is deprecated.

Testing

1. How did you test these changes? Ran the classroom demo and verify that the application rendered correctly.

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