Add DANFE font size configuration

[douglasduarte]

Summary

• Add DanfeFontSizes to configure DANFE font sizes by block/element.
• Add Danfe::setFontSizes(...) and replace hardcoded DANFE font sizes with named element lookups.
• Document usage and add tests for the configuration object and DANFE rendering.

Usage

$danfe = new Danfe($xml);
$danfe->setFontSizes(DanfeFontSizes::fromArray([
    'cabecalho' => [
        'titulo_danfe' => 12,
        'valor' => 9,
    ],
    'itens' => [
        'cabecalho' => 5,
        'dados' => 6,
    ],
]));

Tests

• php -l src/NFe/DanfeFontSizes.php && php -l src/NFe/Danfe.php && php -l tests/NFe/DanfeFontSizesTest.php && php -l tests/NFe/DanfeTest.php
• vendor/bin/phpunit --filter "DanfeFontSizesTest|DanfeTest"

Note: running composer test locally on PHP 8.4 currently reports one unrelated failure in NFePHP\DA\Tests\NFSe\DanfseTest::testUsaIbscbsConsolidadoDaInfNfseQuandoInformado: the generated text contains Base de Cálculo Após Exclusões e Reduções R$ 985,00, while the test expects R$ 777,77.