Ensure new front-end code is picked up by browsers after a release

[rogup]

Once new code has been deployed to a server, browsers need to hit that server to grab the site and its assets. This can be time consuming, so browsers often keep using cached old code. This can lead to bugs, if the old front-end code doesn't match with new assets, as @ColmDC has experienced.

We fixed the same problem on LX by improving the webpack config to use hashes in filenames. See DigitalCommons/land-explorer-front-end#220

The fix is small and easy.