Introducing child reconciliation

[wavesoft]

This PR introduces proper child reconciliation algorithm, keeping the same tiny size. To achieve this, the scope has changed slightly. In detail:

• ADDED: Proper Child Reconciliation

Now only the altered DOM elements are updated, instead of the entire DOM tree:

• REPLACED: Pre-defined tag shorthands

The pre-defined set of tags is now removed. Instead, you need to manually specify the tag names you want to use.

// Previously
R(div('Hello'), document.body);

// Now
const {div} = H;
R(div('Hello'), document.body);

[styfle]

Nice!