tooltip: rework as pseudo-component, fix overflow

uses the <tool-tip> tag now, and the setupTooltips() function in ui.ts
must be called at any point in the pages load. added "below-center"
position, showing below and centered horizontally. breakpoint tailwind
lingo also now works (e.g. "below-center sm:right"). If a left or
right-aligned tooltip clips off the screen, it will be shifted the
appropriate amount left/right to avoid that automatically.

ts/pwr-pin.ts

@@ -1,7 +1,10 @@
 import { toClipboard, notificationBox } from "./modules/common.js";
+import { setupTooltips } from "./modules/ui.js";
 
 declare var window: GlobalWindow;
 
+setupTooltips();
+
 const pin = document.getElementById("pin") as HTMLSpanElement;
 
 if (pin) {