Adds email template layout and formatting

bookwyrm/templates/email/invite/html_content.html

@@ -1,2 +1,17 @@
+{% extends 'email/html_layout.html' %}
 {% load i18n %}
-<a href="{{ invite_link }}">{% blocktrans %}Join {{ site_name }}{% endblocktrans %}</a>
+
+{% block content %}
+<p>
+    {% blocktrans %}You're invited to join {{ site_name }}!{% endblocktrans %}
+</p>
+
+{% trans "Join Now" as text %}
+{% include 'email/snippets/action.html' with path=invite_link text=text %}
+
+<p>
+    {% url 'code-of-conduct' as coc_path %}
+    {% url 'about' as about_path %}
+    {% blocktrans %}Learn more <a href="https://{{ domain }}{{ about_path }}">about this instance</a>.{% endblocktrans %}
+</p>
+{% endblock %}

bookwyrm/templates/email/invite/subject.html

@@ -1,2 +1,2 @@
 {% load i18n %}
-{% blocktrans %}You're invited! Join {{ site_name }}{% endblocktrans %}
+{% blocktrans %}You're invited to join {{ site_name }}!{% endblocktrans %}

bookwyrm/templates/email/invite/text_content.html

@@ -1,2 +1,10 @@
+{% extends 'email/text_layout.html' %}
 {% load i18n %}
-{% blocktrans %}Join {{ site_name }}: {{ invite_link }}{% endblocktrans %}
+{% block content %}
+{% blocktrans %}You're invited to join {{ site_name }}! Click the link below to create an account.{% endblocktrans %}
+
+{{ invite_link }}
+
+{% trans "Learn more about this instance:" %} https://{{ domain }}{% url 'about' %}
+
+{% endblock %}