Clarify that the documentation suggestion form is only for documentation.

docs/_includes/components/suggestion-form.html

@@ -1,12 +1,12 @@
 <h2>Improve this documentation</h2>
 
 <p>Have an idea on how to make this documentation even better? Send your
-feedback below! (But if you need help installing or using borgmatic, please
-use our <a href="https://torsion.org/borgmatic/#issues">issue tracker</a>
-instead.)</p>
+feedback below! But if you need help with borgmatic, or have an idea for a
+borgmatic feature, please use our <a href="https://torsion.org/borgmatic/#issues">issue
+tracker</a> instead.</p>
 
 <form id="suggestion-form">
-    <div><label for="suggestion">Suggestion</label></div>
+    <div><label for="suggestion">Documentation suggestion</label></div>
     <textarea id="suggestion" rows="8" cols="60" name="suggestion"></textarea>
     <div data-sk-error="suggestion" class="form-error"></div>
     <input id="_page" type="hidden" name="_page">