Add a Prime Reminder on sub buttons. Super easy, the data was already there. Also add the Prime crown to the icon font.

src/main.js

@@ -95,7 +95,7 @@ class FrankerFaceZ extends Module {
 FrankerFaceZ.Logger = Logger;
 
 const VER = FrankerFaceZ.version_info = {
-	major: 4, minor: 0, revision: 0, extra: '-beta1.5',
+	major: 4, minor: 0, revision: 0, extra: '-beta1.6',
 	build: __webpack_hash__,
 	toString: () =>
 		`${VER.major}.${VER.minor}.${VER.revision}${VER.extra || ''}${DEBUG ? '-dev' : ''}`

src/sites/twitch-twilight/modules/sub_button.js

@@ -0,0 +1,75 @@
+'use strict';
+
+// ============================================================================
+// Sub Button
+// ============================================================================
+
+import Module from 'utilities/module';
+import {createElement as e} from 'utilities/dom';
+
+export default class SubButton extends Module {
+	constructor(...args) {
+		super(...args);
+
+		this.should_enable = true;
+
+		this.inject('i18n');
+		this.inject('settings');
+		this.inject('site.fine');
+
+		this.settings.add('sub-button.prime-notice', {
+			default: true,
+
+			ui: {
+				path: 'Channel > Metadata >> Subscription',
+				title: 'Show Prime Reminder',
+				description: 'Display a crown on subscription buttons when your free channel sub with Prime is available.',
+				component: 'setting-check-box'
+			},
+
+			changed: () => this.SubButton.forceUpdate()
+		});
+
+		this.SubButton = this.fine.define(
+			'sub-button',
+			n => n.reportSubMenuAction && n.isUserDataReady
+		);
+	}
+
+	onEnable() {
+		this.SubButton.ready(() => this.SubButton.forceUpdate());
+
+		this.SubButton.on('mount', this.updateSubButton, this);
+		this.SubButton.on('update', this.updateSubButton, this);
+	}
+
+
+	updateSubButton(inst) {
+		const container = this.fine.getChildNode(inst),
+			btn = container && container.querySelector('button[data-test-selector="subscribe-button__dropdown"]');
+		if ( ! btn )
+			return;
+
+		const props = inst.props,
+			data = props.data && props.data.user,
+			self = data && data.self,
+			should_show = this.settings.get('sub-button.prime-notice') && self && self.canPrimeSubscribe && ! self.subscriptionBenefit,
+
+			icon = btn.querySelector('.ffz--can-prime');
+
+		if ( should_show && ! icon ) {
+			btn.insertBefore(
+				e('span', 'tw-button__icon tw-button__icon--left ffz--can-prime',
+					e('figure', {
+						className: 'ffz-i-crown ffz-tooltip',
+						'data-tooltip-type': 'html',
+						'data-title': this.i18n.t('sub-button.prime', 'Your free channel sub with Prime is available.')
+					})
+				),
+				btn.firstElementChild
+			);
+
+		} else if ( ! should_show && icon )
+			icon.remove();
+	}
+}