Add basics to README and runnable examples for wiki

[Copilot]

The README had no usage guidance beyond installation — no API examples, no reactive patterns, nothing to help a new user get started. The repo also lacked any runnable demos.

README — new Basics section

Six progressive sections with minimal, illustrative code snippets:

• Building Elements — $html.<tag>(attrs, ...children) call signature
• Attributes & Events — style string/object, onclick/on, data-*
• observable — getter/setter pattern, DOM child binding, attribute binding, two-way <input> binding
• computed & cstr — deriving values from observables; tagged template reactive strings
• arrayObservable — push/splice/reverse + .bind.map() for live lists
• validatable() — isValid computed, inline error messages, disabled submit

// Two-way input binding
const name = observable("");
const input = $html.input({ type: "text", value: name });
const greeting = $html.p((() => `Hello, ${name() || "stranger"}!`).computed(name));

// Reactive array list
const items = arrayObservable(["Apple", "Banana"]);
const list = $html.ul(items.bind.map(item => $html.li(item)));
items.push("Cherry");  // DOM updates in place

examples/ — 10 self-contained HTML demos

Each file loads dist/dom.js via a relative path and runs in-browser with no build step.

Static (dom-builder only):

• 01-hello-world — card element
• 02-static-list — array → <ul>
• 03-contact-form — form + submit handler
• 04-data-table — table from object array
• 05-svg-badge — $svg namespace

Reactive (dom-builder + observable):

• 01-live-counter — observable bound to DOM
• 02-todo-list — arrayObservable, computed, cstr
• 03-live-search — computed filter + match highlight
• 04-registration-form — validatable(), computed errors, disabled submit
• 05-optimistic-like — observable.optimistic() with automatic rollback on simulated server failure

An examples/index.html links all demos; README's new More Examples table points into the directory.