Use an auto PHP generator for functions documentation

[corsacca]

I did a test of the prominent PHP documentation generator: PHP Documentor. You can see what it has generated at https://dt-docs-demo.firebaseapp.com/.
I copied one of the default templates and made a small change to update the subheading of the site to say “D.T Documentation” (as a test of customizing it). You can see the code at DiscipleTools/disciple-tools-theme@master...cairocoder01:php-documentor
I can also foresee adding some custom wiki content within the codebase that we could use a markdown-to-html utility to copy within the same docs site. All of that could be automated in a Github Action for whenever a new release is made and deployed to any static hosting site (this example is on Firebase, but we could use the github.io static hosting as well. Both are free).