jQuery 3.5.1
htmLawed 1.2.5
PHPMailer 5.2.28

Replace id with an options parameter, add template option

Use class/method for each ‘page script.’
Add controller for user list pages.

Fixes #540

Also add canonical tag to question lists and tag pages.

We now use qa-global.js for all the in-page JS (except for qa-admin.js
which regular visitors don’t need).

Clean up some of the JS code