Set up folder structure and stubs for beta doc site using furo theme.

Squash merge Includes:
- Fill out folder structure for all TOC sections. Complete AdaRound example.
- Make beta doc build optional for agile development.
- Stripped beta piccolo theme CSS down to only modifications of the stock theme CSS.
- Swap in furo theme for look & feel and right-side menu.
- Refine furo theme options.
- More mods to furo theme. Set up index for API ref.

Signed-off-by: Dave Welsch <dwelsch@expertsupport.com>

Docs/beta/_static/aimet-furo.css

@@ -0,0 +1,32 @@
+
+ aside.toc-drawer ul ul ul ul {
+   display: none;
+}
+
+.toctree-l3 {
+    display: none;
+}
+
+[for^="toctree-checkbox-"], [id^="toctree-checkbox-"] {
+    visibility: hidden;
+}
+
+/* 
+<li class="toctree-l1 current has-children current-page">
+<a class="current reference internal" href="#">AIMET Feature Guide</a>
+<input checked="" class="toctree-checkbox" id="toctree-checkbox-1" name="toctree-checkbox-1" role="switch" type="checkbox">
+    <label for="toctree-checkbox-1">
+        <div class="visually-hidden">Toggle navigation of AIMET Feature Guide</div>
+        <i class="icon">
+            <svg>
+                <use href="#svg-arrow-right">
+                </use>
+            </svg>
+        </i>
+    </label>
+    <ul>
+        <li class="toctree-l2">
+            <a class="reference internal" href="qat.html">Quantization aware training</a>
+        </li>
+    </ul>
+*/