Update sponsors

docs/_sass/book.sass

@@ -13,7 +13,7 @@ $book-beige: #FFEDD7
     transform: scale(1)
 
 .bd-book-banner
-  background-color: $white-bis
+  background-color: $primary
   position: relative
 
 .bd-book-pattern,

docs/_sass/expo.sass

@@ -48,10 +48,8 @@
     flex-wrap: wrap
     justify-content: space-between
   .bd-website
-    margin-top: 3rem
+    margin-bottom: 3rem
     width: calc(50% - 3rem)
-    &:nth-child(1)
-      margin-top: 0
     &.bd-is-highlighted
       width: 100%
   .bd-website-image

docs/_sass/footer.sass

@@ -38,7 +38,7 @@
 
 .bd-footer-support
   @extend %bd-footer-box
-  border-top: none
+  border-top: 2px solid $white-ter
   box-shadow: none
   padding: 3rem
   .bd-footer-title
@@ -50,6 +50,10 @@
 .bd-footer-donation
   flex: none
 
+.bd-footer-sponsor a
+  @extend %center
+  height: 70px
+
 +tablet
   .bd-footer-donation
     width: 240px