feat: revamp email templates to be more style agnostic (#7375)

* feat: re-designed digest

Updated design, logic no longer shows "no topics", just doesn't
show the list at all, teaser re-retrieved for digest so that it
always grabs a teaser even if there is no reply, changed default
email background to a light grey.

* fix: minor padding issues in digest

* fix: banned template

* fix: invitation.tpl

* fix: removed unused notif_chat and notif_post email templates

* fix: notification template

* fix: registration_accepted template

* fix: reset tpl

* fix: test tpl

* fix: email verify tpl

* fix: reset notify tpl

* fix: welcome tpl

* fix: additional minor font fixes

* fix: removed unused email header image assets

* fix: internationalised 'your daily digest' string

* fix: broken url in digest 🤦

* feat: added RTL support for emailer

/cc @PostMidnight

src/topics/teaser.js

@@ -23,6 +23,7 @@ module.exports = function (Topics) {
 		var teaserPids = [];
 		var postData;
 		var tidToPost = {};
+		const teaserPost = this ? this.teaserPost : meta.config.teaserPost;
 
 		topics.forEach(function (topic) {
 			counts.push(topic && topic.postcount);
@@ -30,9 +31,9 @@ module.exports = function (Topics) {
 				if (topic.teaserPid === 'null') {
 					delete topic.teaserPid;
 				}
-				if (meta.config.teaserPost === 'first') {
+				if (teaserPost === 'first') {
 					teaserPids.push(topic.mainPid);
-				} else if (meta.config.teaserPost === 'last-post') {
+				} else if (teaserPost === 'last-post') {
 					teaserPids.push(topic.teaserPid || topic.mainPid);
 				} else { // last-reply and everything else uses teaserPid like `last` that was used before
 					teaserPids.push(topic.teaserPid);