added pace demo & pace override

- created pages/examples/pace.html
- created build/scss/plugins/_pace.scss with color overrides
- created docs/components/plugins.md with plugin overrides & extra styles
- updated docs sidebar menu
- updated demo sidebar menu with pace demo link

pages/examples/projects.html

@@ -559,6 +559,12 @@
                   <p>Error 500</p>
                 </a>
               </li>
+              <li class="nav-item">
+                <a href="../examples/pace.html" class="nav-link">
+                  <i class="far fa-circle nav-icon"></i>
+                  <p>Pace</p>
+                </a>
+              </li>
               <li class="nav-item">
                 <a href="../examples/blank.html" class="nav-link">
                   <i class="far fa-circle nav-icon"></i>