Add a small sentence about the parameter values

Author: agriyakhetarpal

layouts/shortcodes/grid.html

@@ -186,6 +186,14 @@
 
 {{< /grid >}}
 
+The parameters are based on sphinx-design system grid utilities, which is in-turn based on Bootstrap grid system. They are as follows:
+- 0: 0 (no spacing)
+- 1: 0.25rem
+- 2: 0.5rem (default)
+- 3: 1rem
+- 4: 1.5rem
+- 5: 3rem
+
 */}}
 
 {{- $items := "" -}}