Add new container docs

sass/elements/container.sass

@@ -1,4 +1,5 @@
 $container-offset: (2 * $gap) !default
+$container-max-width: $fullhd !default
 
 .container
   flex-grow: 1
@@ -6,19 +7,21 @@ $container-offset: (2 * $gap) !default
   position: relative
   width: auto
   &.is-fluid
-    max-width: none
+    max-width: none !important
     padding-left: $gap
     padding-right: $gap
     width: 100%
   +desktop
     max-width: $desktop - $container-offset
   +until-widescreen
-    &.is-widescreen
-      max-width: $widescreen - $container-offset
+    &.is-widescreen:not(.is-max-desktop)
+      max-width: min($widescreen, $container-max-width) - $container-offset
   +until-fullhd
-    &.is-fullhd
-      max-width: $fullhd - $container-offset
+    &.is-fullhd:not(.is-max-desktop):not(.is-max-widescreen)
+      max-width: min($fullhd, $container-max-width) - $container-offset
   +widescreen
-    max-width: $widescreen - $container-offset
+    &:not(.is-max-desktop)
+      max-width: min($widescreen, $container-max-width) - $container-offset
   +fullhd
-    max-width: $fullhd - $container-offset
+    &:not(.is-max-desktop):not(.is-max-widescreen)
+      max-width: min($fullhd, $container-max-width) - $container-offset