mention about proton mail during signup (#1796)

* mention about proton mail during signup

* format

* trim whitespaces

---------

Co-authored-by: Son NK <son@sons-macbook-air-2.home>
Co-authored-by: Son NK <son@Sons-MacBook-Air-2.local>

CONTRIBUTING.md

@@ -169,6 +169,12 @@ For HTML templates, we use `djlint`. Before creating a pull request, please run
 poetry run djlint --check templates
 ```
 
+If some files aren't properly formatted, you can format all files with
+
+```bash
+poetry run djlint --reformat .
+```
+
 ## Test sending email
 
 [swaks](http://www.jetmore.org/john/code/swaks/) is used for sending test emails to the `email_handler`.

templates/auth/register.html

@@ -9,10 +9,13 @@
       <h1 class="card-title">Create new account</h1>
       <div class="form-group">
         <label class="form-label">Email address</label>
-        {{ form.email(class="form-control", type="email") }}
+        {{ form.email(class="form-control", type="email", placeholder="YourName@protonmail.com") }}
         <div class="small-text alert alert-info" style="margin-top: 1px">
           Emails sent to your alias will be forwarded to this email address.
+          <br>
           It can't be a disposable or forwarding email address.
+          <br>
+          We recommend using a <a href="https://proton.me/mail" target="_blank">Proton Mail</a> address
         </div>
         {{ render_field_errors(form.email) }}
       </div>

templates/single.html

@@ -5,7 +5,7 @@
   <div class="page-single">
     <div class="container">
       <div class="row">
-        <div class="col mx-auto" style="max-width: 28rem">
+        <div class="col mx-auto" style="max-width: 32rem">
           <div class="text-center mb-6">
             <a href="{{ LANDING_PAGE_URL }}">
               <img src="/static/logo.svg"