five common positions for expressions in Lit templates
<!-- Child nodes -->
<h1>${this.pageTitle}</h1>
<!-- Attribute -->
<div class=${this.myTheme}></div>
<!-- Boolean attribute -->
<p ?hidden=${this.isHidden}>I may be in hiding.</p>
<!-- Property -->
<input .value=${this.value}>
<!-- Event listener -->
<button @click=${() => {console.log("You clicked a button.")}}>...</button>