Long-overdue Upgrades

My cloud hosting provider recently informed me that I was using a version of PHP that would shortly be going out of support, so I've learned how to upgrade the site to use a more recent PHP version. It turned out to be a very simple process via their cloud hosting control panel, so I can update that more often in future.

At the same time, I made some changes to the site's configuration to improve security, including HTTP Strict Transport Security and a new Content Security Policy. I also added some new links to services that I use and recommend.