Refactor twig component syntax

[weaverryan]

Hi!

Thanks again for getting this rolling! The regex was working great, but it didn't give us any opportunity to give the user a good error if they make a small mistake. This is an attempt to rewrite the logic without regex. It's possible I've missed something (though tests pass). And probably a lot more edge case tests could be added & probably we should try to "mess up" Twig syntax a bunch of times to make sure we get good errors (and ideally write tests for those errors).

This also adds the concept of a "default" block:

<t:successAlert type="{{ alertType }}">
    <p>It's a small world after all</p>
    <t:successAlert type="success">Inception!</t:successAlert>

    <t:block name="some_other_block">
        Not used
    </t:block>
</t:successAlert>

In this case, the content that is NOT inside the <t:block (so the <p> tag + the embedded <t:successAlert type="success">Inception!</t:successAlert>) become part of a new block called default:

<div{{ attributes.defaults({class: 'alert alert-'~type}) }}>
    {% block default %}{% endblock %}
</div>

🔥

[WebMamba]

Woooow Thanks for your work on this Ryan! 🚀 After your comment on getting better errors on small developer mistakes, I was spinning my head. And I came to the same conclusion as you: regex is not the way to go, and we need to reproduce what the twig Lexer does!

[WebMamba]

Sorry, I just push on the previous branch just before your opened this PR.