New way to present ROOT examples in a gallery

Author: couet

_includes/example-list

@@ -0,0 +1,30 @@
+{% assign tutorials_list = page[include.id] %}
+{% assign ref_guide_url = "https://root.cern/doc/master/" %}
+
+<table id="navtable">
+  {% assign i = 0 %}
+  {% for tut in tutorials_list %}
+    {% if i==0 %}
+      <tr>
+    {% endif %}
+    <td>
+      <a href="{{ ref_guide_url }}{{ tut.example | replace: '.C', '_8C'}}.html">
+        <img src="{{ ref_guide_url }}pict1_{{ tut.example }}.png" >
+      </a>
+    <em>
+    {% if tut.title %}{{ tut.title }}{% endif %}
+    </em>
+    </td>
+    {% if i==2 %}
+      </tr>
+    {% endif %}
+    {% assign i = i | plus:1 %}
+    {% if i==3 %}
+      {% assign i = 0 %}
+    {% endif %}
+  {% endfor %}
+  {% if i!=0 %}
+    </tr>
+  {% endif %}
+</table>
+

gallery/index.md

@@ -3,6 +3,20 @@ title: Galleries of images produced with ROOT
 layout: single
 toc: true
 toc_sticky: true
+list1:
+  - example: thstackcolorscheme.C
+    title: This example demonstrates how to use the accessible color schemes with THStack.
+  - example: ratioplot1.C
+    title: Example creating a simple ratio plot of two histograms using the pois division option.
+  - example: fillrandom.C
+    title: Fill a 1-D histogram from a parametric function.
+list2:
+  - example: annotation3d.C
+    title: This example show how to put some annotation on a 3D plot using 3D polylines.
+  - example: exclusiongraph.C
+    title: Draw three graphs with an exclusion zone.
+  - example: graphShade.C
+    title: Show how to shade an area between two graphs
 gallery1:
   - url: /gallery/higgs_plots/Atlas_CLs_Exclusion.png
   - url: /gallery/higgs_plots/Atlas_Data_MC_Comparison.png
@@ -125,6 +139,19 @@ gallery5:
   - url: /gallery/visualisation_techniques_and_basics_graphics/Two_legos_plots_combined.gif
 ---
 
+## Simple examples - UNDER CONSTRUCTION
+
+Overview of various common functionalities  provided by ROOT
+
+### Histograms Examples
+
+{% include example-list id="list1" %}
+
+### Graphs Examples
+
+{% include example-list id="list2" %}
+
+
 ## Higgs Plots
 
 This gallery shows some of the plots (produced using ROOT) presented when the Higgs boson