rpg-cards/generator/components/card-contents.html

<template id="card-contents">
    <style>

        :host {
            padding: 6px;
            border-radius: 6px;
            background-color: white;
            border-color: inherit;
            display: flex;
            flex-direction: column;
            flex: 1;
            font-size: inherit;
        }

    </style>

    <content></content>

</template>

<script>
    (function (window, document) {
        var elemName = 'card-contents';
        var mainDoc = document;
        var importDoc = document.currentScript.ownerDocument;

        var proto = Object.create(HTMLElement.prototype);
        proto.createdCallback = function () {
            var template = importDoc.getElementById(elemName);
            var clone = mainDoc.importNode(template.content, true);
            var root = this.createShadowRoot();
            root.appendChild(clone);
        }

        mainDoc.registerElement(elemName, { prototype: proto });

    })(window, document);
</script>