Reorganize and rewrite examples

This commit is a large-ish scale reorganization of our examples. The
main goal here is to have a dedicated section of the guide for example,
and all examples will be listed there. Each example's `README` is now
just boilerplate pointing at the guide along with a blurb about how to
run it.

Some examples like `math` and `smorgasboard` have been deleted as they
didn't really serve much purpose, and others like `closures` have been
rewritten with `web-sys` instead of hand-bound bindings.

Overall it's hoped that this puts us in a good and consistent state for
our examples, with all of them being described in the guide, excerpts
are in the guide, and they're all relatively idiomatically using
`web-sys`.

examples/char/index.js

@@ -1,5 +1,5 @@
 /* eslint-disable no-unused-vars */
-import {chars} from './chars.js';
+import { chars } from './chars-list.js';
 let imp = import('./char.js');
 let mod;
 
@@ -71,4 +71,4 @@ function newField(key, value) {
     val.appendChild(document.createTextNode(value));
     ret.appendChild(val);
     return ret;
-}
+}