feat: plea for help plus bug fixes

1.  Add plea for help to header.
2.  Change background color temporarily to match logo.
3.  Add Cthulhu logo source to colophon.
4.  Fix links in colophon.

_data/colophon.yml

@@ -1,18 +1,18 @@
 - key: "atkinson"
-  value: "https://brailleinstitute.org/freefont"
+  url: "https://brailleinstitute.org/freefont"
 - key: "draw-io"
-  value: "https://www.drawio.com/"
+  url: "https://www.drawio.com/"
 - key: "ghp"
-  value: "https://pages.github.com/"
+  url: "https://pages.github.com/"
 - key: "highlight-css"
-  value: "https://numist.github.io/highlight-css/"
+  url: "https://numist.github.io/highlight-css/"
 - key: "jekyll"
-  value: "https://jekyllrb.com/"
+  url: "https://jekyllrb.com/"
 - key: "plausible"
-  value: "https://plausible.io/"
+  url: "https://plausible.io/"
 - key: "rouge"
-  value: "https://rouge.jneen.net/"
+  url: "https://rouge.jneen.net/"
 - key: "stamps"
-  value: "https://third-bit.com/colophon/"
+  url: "https://third-bit.com/colophon/"
 - key: "wave"
-  value: "https://wave.webaim.org/"
+  url: "https://wave.webaim.org/"

colophon.md

@@ -21,5 +21,6 @@ which provides a lightweight ethical alternative to surveillance capitalism.
 The colors in this theme
 are lightened versions of those used in
 [classic Canadian postage stamps][stamps].
+Cthulhu logo taken from <a href="https://www.deviantart.com/lockox2/art/Cthulhu-279575365">DeviantArt</a>
 
 {% include links.md links=site.data.colophon %}

index.md

@@ -3,6 +3,31 @@ home: true
 ---
 {% include init_counters.md %}
 
+<div class="row">
+  <div class="col-6 center">
+    <img src="{{root}}/res/cthulhu-300x253.jpg" alt="stylized Cthulhu"/>
+  </div>
+  <div class="col-6">
+    <p>
+      <a href="{{site.data.tutorial.repo}}/issues/"><strong>The Querynomicon Needs Your Help</strong></a>
+    </p>
+    <ol>
+      <li>
+        <p><em>More exercises</em> to help learners practice.</p>
+      </li>
+      <li>
+        <p><em>Sample solutions</em> so that they can check their work.</p>
+      </li>
+      <li>
+        <p><em>CSS show/hide for solutions</em> because He Who Lies Dreaming said, "No JavaScript."</p>
+      </li>
+      <li>
+        <p><em>Ideas for <a href="https://github.com/gvwilson/sys-tutorial/issues/1">the next tutorial</a></em> because why stop learning now?</p>
+      </li>
+    </ol>
+  </div>
+</div>
+
 <!-- ---------------------------------------------------------------- -->
 {% include section_start.md class="aside" title="What This Is" %}
 
@@ -61,7 +86,7 @@ home: true
 -   Each DBMS stores data in its own way
     -   SQLite stores each database in a single file
     -   [PostgreSQL][postgresql] spreads information across many files for higher performance
--   DBMS can be a library embedded in other programs (SQLite) or a server ([PostgreSQL][postgresql])
+-   DBMS can be a library embedded in other programs (SQLite) or a server (PostgreSQL)
 -   A <a href="#g:rdbms">relational database management system</a> (RDBMS) stores data in tables and uses [SQL][sql] for queries
     -   Unfortunately, every RDBMS has its own dialect of SQL
 -   There are also <a href="#g:nosql">NoSQL databases</a> like [MongoDB][mongodb] that don't use tables
@@ -833,7 +858,7 @@ Reorganize the penguins database:
 Tools like [Sqitch][sqitch] can manage changes to database schemas and data
 so that they can be saved in version control
 and rolled back if they are unsuccessful.
-Translate the changes made by the scripts above into [Sqitch][sqitch].
+Translate the changes made by the scripts above into Sqitch.
 Note: this exercise may take an hour or more.
 
 <!-- ---------------------------------------------------------------- -->

res/tutorial.css

@@ -131,6 +131,7 @@ html {
 body {
     margin-left: var(--large-spacing);
     max-width: var(--page-width);
+    background-color: #FFFFF3;
 }
 
 /*