rename site-side-menu.js to main.js.

Because the amount of JavaScript I've written, it doesn't make sense
to separate things out into their own files yet. So, I've renamed the
file to main.js and will add the little sprinkles of JavaScript
here. If the amount of JavaScript grows, I will need to move things
out of here but that is a future problem.

static/js/main.js

@@ -7,3 +7,7 @@ function toggleSiteSideMenu() {
 	    document.getElementById("be-site-side-menu").style.display = "flex";
 	}
 }
+
+function closeAlert() {
+    document.getElementById("be-alert-container").style.display = "none";
+}