How to include SVG in a block markup? I'm building a custom markup for a block but the SVG part is not rendered. Everything else is rendered correctly.

class HomeSocial extends BlockBase
{

    /**
     * {@inheritdoc}
     */
    public function build()
    {
        $markup = '&lt;div id="container"&gt;';
        $markup .= '&lt;svg width="26.383960" height="21.428597" viewBox="0.736608 -42.857194 26.383960 21.428597"
xmlns="http://www.w3.org/2000/svg"&gt;
&lt;path d="M27.120568 -40.312548C26.149585 -39.894021 25.094896 -39.592681 24.006725 -39.475493C25.128378 -40.145137 25.982174 -41.199826 26.383960 -42.455408C25.346012 -41.835987 24.174136 -41.383978 22.952036 -41.149603C21.964312 -42.204291 20.558060 -42.857194 19.001139 -42.857194C16.004483 -42.857194 13.593766 -40.429736 13.593766 -37.449821C13.593766 -37.031294 13.643989 -36.612767 13.727695 -36.210981C9.241082 -36.445356 5.239962 -38.588216 2.578128 -41.869470C2.109378 -41.065897 1.841520 -40.145137 1.841520 -39.140672C1.841520 -37.265669 2.795762 -35.608301 4.252237 -34.637318C3.364959 -34.670800 2.527905 -34.921917 1.808038 -35.323703C1.808038 -35.306962 1.808038 -35.273480 1.808038 -35.256738C1.808038 -32.628387 3.666299 -30.452045 6.143981 -29.949812C5.691971 -29.832625 5.206479 -29.765660 4.720988 -29.765660C4.369425 -29.765660 4.034603 -29.799143 3.699781 -29.849366C4.386166 -27.706506 6.378356 -26.149585 8.755591 -26.099361C6.897330 -24.642887 4.570318 -23.789091 2.042413 -23.789091C1.590404 -23.789091 1.171876 -23.805832 0.736608 -23.856055C3.130584 -22.315875 5.976570 -21.428597 9.040189 -21.428597C18.984398 -21.428597 24.425252 -29.665214 24.425252 -36.813660C24.425252 -37.048035 24.425252 -37.282411 24.408511 -37.516786C25.463200 -38.286876 26.383960 -39.241118 27.120568 -40.312548ZM27.120568 -40.312548"&gt;&lt;/path&gt;&lt;/svg&gt;';
        $markup .= '&lt;/div&gt;';

        return array(
            '#markup' =&gt; $markup,
            '#cache' =&gt; array(
                'max-age' =&gt; 3600,
            ),
        );
    }


Do I neet to allow SVG tag somewhere in the configuration?
Use inline_template instead of markup, or a theme function (as suggested by Ivan Jaros in a comment also).
Refer to class InlineTemplate for way more details. Here is a partial quote of it:

Provides a render element where the user supplies an in-line Twig template.
Properties:

#template: The inline Twig template used to render the element.
#context: (array) The variables to substitute into the Twig template. Each variable may be a string or a render array.

Usage example:
$build['hello']  = [
  '#type' =&gt; 'inline_template',
  '#template' =&gt; &quot;{% trans %} Hello {% endtrans %} &lt;strong&gt;{{name}}&lt;/strong&gt;&quot;,
  '#context' =&gt; [
    'name' =&gt; $name,
  ]
];