Build using webpack >=5, because webpack ^4 is no longer updating its node compat thing

[mvasilkov]

Tracked here: webpack/node-libs-browser#68

WA: npm install buffer in webpack's node_modules

[mvasilkov]

This is what works on my machine:

cd /usr/local/lib/node_modules/webpack/node_modules/node-libs-browser
npm install buffer@latest