Add donation info to transactional emails. (#1202)

# What it does

Adds a notice to the mailer layout that prompts recipients to donate to
the tool library. Fixes #1195.

# Why it is important

We're missing an opportunity to engage make it as easy as possible to
support the tool library.

# UI Change Screenshot

Before:
![image
(1)](https://github.com/chicago-tool-library/circulate/assets/3331/82c0195a-8dcb-4656-a95d-55e7ea7b72c4)

After:

![image](https://github.com/chicago-tool-library/circulate/assets/3331/0187a313-ff65-4f54-9d90-cfa808d80fcb)

# Implementation notes

* I also tweaked the styles of the various banners to remove the heavy
outlines. With 3 banners it seemed really distracting to me.

# Your bandwidth for additional changes to this PR

_Please choose one of the following to help the project maintainers
provide the appropriate level of support:_

- [x] I have the time and interest to make additional changes to this PR
based on feedback.
- [ ] I am interested in feedback but don't need to make the changes
myself.
- [ ] I don't have time or interest in making additional changes to this
work.
- [ ] Other or not sure (please describe):

app/views/layouts/mailer.html.mjml

@@ -22,14 +22,16 @@
       }
     </mj-style>
     <mj-style>
+      .donation {
+        background: #FFEADE;
+        padding: 1em;
+      }
       .warning {
-        border: solid 3px gold;
         background: lemonchiffon;
         padding: 1em;
         margin-bottom: 1em;
       }
       .info {
-        border: solid 3px #67C4E3;
         background: aliceblue;
         padding: 1em;
       }
@@ -62,6 +64,16 @@
         </mj-text>
       </mj-column>
     </mj-section>
+
+    <mj-section>
+      <mj-column>
+        <mj-text>
+          <div class="donation">
+            <%= render partial: "member_mailer/donation" -%> 
+          </div>
+        </mj-text>
+      </mj-column>
+    </mj-section>
 
     <% if @preview || !@library.email_banner1.blank? %>
       <mj-section>

app/views/layouts/mailer.text.erb

@@ -1,4 +1,7 @@
 <%= yield %>
+
+<%= HTMLToMarkdown.new.convert(render partial: "member_mailer/donation", formats: [:html]) -%> 
+
 <% unless @library.email_banner1.blank? %>
 
 ** <%= HTMLToMarkdown.new.convert(@library.email_banner1).strip -%> **

app/views/member_mailer/_donation.html.erb

@@ -0,0 +1,5 @@
+<strong>Did the Tool Library help you accomplish a project?</strong> Make a small donation to keep us going!
+You can <%# erblint:disable TrailingWhitespace %>
+<a href="https://chicagotoollibrary.app.neoncrm.com/forms/18">donate by credit card, Apple Pay, or ACH</a>, and we also have <%# erblint:disable TrailingWhitespace %>
+<a href="https://www.venmo.com/u/ChiToolLibrary">Venmo</a> and <%# erblint:disable TrailingWhitespace %>
+<a href="https://www.paypal.com/donate/?hosted_button_id=7X45CFLZMKBLY">PayPal</a> accounts if that's more your speed.