Ghost/ghost/admin/app/components/custom-theme-settings/text.hbs

<div class="gh-stack-item {{if (eq @index 0) "gh-setting-first" "gh-setting"}}">
    <div class="flex-grow-1">
        <label class="gh-setting-title gh-theme-setting-title" for={{this.inputId}}>
            {{humanize-setting-key @setting.key}}
        </label>

        <input
            type="text"
            class="gh-input"
            value={{@setting.value}}
            id={{this.inputId}}
            name={{this.inputName}}
            {{on "input" this.updateValue}}
            {{on "blur" this.triggerOnChange}}
        />
    </div>
</div>