* OBGM-365 Update mini-css-extract-plugin, and other plugins to match.
mini-css-extract-plugin began targeting both Webpack 4 and Webpack 5
as of release 0.11.0; at that time it started testing against 5-only
releases. This commit updates mini-css-extract-plugin to the most
recent Webpack-4-only release, and css-loader and file-loader to
the latest major releases against which mini-css-extract-plugin was
built and tested.
* OBGM-365 Apply a node security fix; log node/npm version info when building.
* OGBM-365 Cache build intermediates in the working directory (not $HOME).
