Add basic docs on arpeggiator plugins for 8.0

include/bundled-plugins-utilities.html

@@ -144,3 +144,63 @@
     MIDI Note Mapper
   </figcaption>
 </figure>
+
+<h2>Arpeggiators</h2>
+
+<p>
+  Arpeggiators commonly take a chord and play it note by note in a certain
+  pattern: up (from the lowest note to the highest note),  down (from the
+  highest note to the lowest one), up and down, down and up, or in a random
+  fashion.
+</p>
+
+<p>
+  They also have a number of additional settings like division that
+  defines the rate at which an arpeggiator will repeat the pattern. Or the
+  number of octaves the arpeggiator will jump between while transposing
+  a repeating note.
+</p>
+
+<p>
+  All three arpeggiators shipped with Ardour&nbsp;— simple arpeggiator, Barlow
+  arpeggiator, and Raptor arpeggiator&nbsp;— share these basic settings.
+  However, some of their design specifics vary.
+</p>
+
+<p>
+  The simple arpeggiator allows setting different velocities for notes at the
+  bar line, beat line, and subdivisions. It also has a swing setting.
+</p>
+
+<figure>
+  <img style="width:50%;" src="/images/plugins-arpeggiator-simple.png" alt="Simple arpeggiator">
+  <figcaption>
+    Simple arpeggiator
+  </figcaption>
+</figure>
+
+<p>
+  The Barlow arpeggiator has sample-accurate triggering and automatically
+  adjusts to the current time signature. It also allows setting min and max
+  velocity.
+</p>
+
+<figure>
+  <img style="width:50%;" src="/images/plugins-arpeggiator-barlow.png" alt="Barlow arpeggiator">
+  <figcaption>
+    Barlow arpeggiator
+  </figcaption>
+</figure>
+
+
+<p>
+  The Raptor arpeggiator has harmonic controls, input pitch and velocity
+  tracking, and a few other features.
+</p>
+
+<figure>
+  <img style="width:50%;" src="/images/plugins-arpeggiator-raptor.png" alt="Raptor arpeggiator">
+  <figcaption>
+    Raptor arpeggiator
+  </figcaption>
+</figure>