[IMP] website: replace snippet thumbnails with better ones

addons/website/views/snippets.xml

@@ -619,7 +619,7 @@
                     <t t-snippet="website.s_well" t-thumbnail="/website/static/src/img/blocks/block_well.png"/>
                     <t t-snippet="website.s_panel" t-thumbnail="/website/static/src/img/blocks/block_panel.png"/>
                     <t t-snippet="website.s_image_floating" t-thumbnail="/website/static/src/img/blocks/block_text_image.png"/>
-                    <t t-snippet="website.s_share" t-thumbnail="/website/static/src/img/blocks/block_button.png"/>
+                    <t t-snippet="website.s_share" t-thumbnail="/website/static/src/img/blocks/block_share.png"/>
                 </div>
             </div>
 
@@ -633,7 +633,7 @@
                     <t t-snippet="website.s_button" t-thumbnail="/website/static/src/img/blocks/block_button.png"/>
                     <t t-snippet="website.s_references" t-thumbnail="/website/static/src/img/blocks/block_references.png"/>
                     <t t-snippet="website.s_faq_collapse" t-thumbnail="/website/static/src/img/blocks/block_faq.png"/>
-                    <t t-snippet="website.s_feature_grid" t-thumbnail="/website/static/src/img/blocks/block_three_columns.png"/>
+                    <t t-snippet="website.s_feature_grid" t-thumbnail="/website/static/src/img/blocks/block_feature_grid.png"/>
                 </div>
             </div>