Move calendar inline Javascript from HTML partials to JS files

[carrythebanner]

Our main calendar Javascript is in the theme's /assets/js/cal folder. However, there is also some JS inline in HTML partials, in the theme's /layouts/partials/cal directory:

• events.html
• fullcal.html
• up-next.html
• pp-2020-cal.html
• scripts.html
• and maybe others?

We should get that JS code out of those HTML partials and into JS files, which would make it clearer where all of the JS actually lives (and also makes it easier to minify them).

Note that Hugo variables probably can't be accessed within plain JS files. But we might want to refactor uses of that anyway, as it muddies the line between the Hugo site and our calendar client.