add config option to columns posts block and posts grid

assets/sass/_theme/_configuration.sass

@@ -220,7 +220,7 @@ $icons: map-merge($icons, ("twitter": "\e90d"))
 
 // Breakpoints
 // TODO: réécrire en sass les mixins bootstrap
-$grid-breakpoints: (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px, xxl: 1440px)  !default
+$grid-breakpoints: (xs: 0, sm: 576px, md: 992px, lg: 1024px, xl: 1200px, xxl: 1440px)  !default
 
 // System
 
@@ -264,6 +264,9 @@ $block-pages-card-page-color: $color-text !default
 $block-pages-card-page-background-hover: $color-accent !default
 $block-pages-card-page-color-hover: $color-background !default
 
+// Block posts
+$block-posts-grid-columns: 3 !default
+
 // Block timeline
 $block-timeline-horizontal-background: $color-background-alt !default
 $block-timeline-horizontal-color: $color-text !default
@@ -311,6 +314,7 @@ $article-media-aspect-ratio: 2 !default
 $post-media-background: $article-media-background !default
 $post-categories-color: color-contrast($color-text, 20%) !default
 $post-time-color: $color-text-alt !default
+$posts-grid-columns: $block-posts-grid-columns !default
 
 // Person
 $persons-avatar-background-color: $color-background-alt !default

assets/sass/_theme/blocks/posts.sass

@@ -6,7 +6,7 @@
             text-decoration: none
     .posts
         @include grid(1)
-        @include grid(3, md)
+        @include grid($block-posts-grid-columns, md)
     article
         h1
             a
@@ -27,7 +27,7 @@
                     @include grid(2, md, $grid-gutter, half($grid-gutter))
             @include in-page-without-sidebar
                 .grid
-                    @include grid(3)
+                    @include grid($block-posts-grid-columns)
     &--list
         article
             border-bottom: 1px solid $color-border

assets/sass/_theme/sections/posts.sass

@@ -50,7 +50,7 @@
         .posts
             @include grid(1)
             @include grid(2, md)
-            @include grid(3, xxl)
+            @include grid($posts-grid-columns, xxl)
 
 .categories__term
     @if $posts-layout-list