add SCREEN_SIZE const

src/config/variables.js

@@ -1,3 +1,15 @@
+// Bootstrap 3 breakpoints
+/* XS - Extra Small Devices, Phones */
+/* SM - Small Devices, Tablets */
+/* MD - Medium Devices, Desktops */
+/* LG - Large Devices, Wide Screens */
+export const SCREEN_SIZE = {
+    XS: '480px',
+    SM: '768px',
+    MD: '992px',
+    LG: '1170px',
+};
+
 //  OLD UNITS
 // SMALLEST: '10px',
 // SMALLER: '12px',
@@ -13,7 +25,6 @@
 // H3: '14px',
 // H4: '12px',
 // COUNTER: '11px',
-
 export const FONT_SIZE = {
     SMALL: '0.8571rem',
     BASE: '1rem',