Add Fullscreen in viewer, Track links with Google Analytics, Use .env file

- Fullscreen is a component that watches a store value set by the Carousel component on a picture click
- Use a .env file for API and website related settings and informations
- Google Analytics is now in place, tracking each routes link and viewer photo change

src/style/pages/_viewer.scss

@@ -44,17 +44,17 @@
                 display: none;
             }
         }
+    }
 
-        // Buttons
-        .buttons {
-            display: flex;
+    // Buttons
+    &__buttons {
+        display: flex;
 
-            a {
-                margin-left: 16px;
+        a {
+            margin-left: 16px;
 
-                &:first-child {
-                    margin-left: 0;
-                }
+            &:first-child {
+                margin-left: 0;
             }
         }
     }
@@ -86,10 +86,8 @@
             right: 0;
 
             // Specific box shadow for images
-            &__images {
-                &--photo {
-                    box-shadow: 0 pxVW(16px) pxVW(40) rgba(#2E025C, 0.4);
-                }
+            &__photo {
+                box-shadow: 0 pxVW(16px) pxVW(40) rgba(#2E025C, 0.4);
             }
         }