Upgrade to Webpack v5

As seen in !77932 (comment 807910116), Webpack v4 still uses MD4 as a hashing algorithm.

Webpack 5.54.0 added the ability to change hash functions to something like SHA256 (https://github.com/webpack/webpack/pull/14306), but we need to upgrade to this version to become FIPS compliant.

Upgrade guide: https://github.com/webpack/changelog-v5/blob/master/MIGRATION%20GUIDE.md

/cc: @dorrino, @mikegreiling