feat(scss): Add bootstrap-5-like grids & media queries

This branch is just for "good to have" optional stand-alone sass features.

In this commit, I aimed to make some things more like bootstrap 5 for ease of use. I  changed the grid breakpoints to match that of Bootstrap 5's and added media query mixins that are more logical like in bootstrap 5.

falcon/_dev/css/abstracts/variables/bootstrap/_grid.scss

@@ -1,3 +1,21 @@
-$grid-columns:                12;
-$grid-gutter-width:           rem-calc(20px);
-$grid-row-columns:            6;
+// Made this more like the breakpoints used in Bootstrap 5
+$grid-breakpoints: (
+    xs: 0,
+    sm: 576px,
+    md: 768px,
+    lg: 992px,
+    xl: 1200px,
+    xxl: 1400px,
+);
+
+$container-max-widths: (
+    sm: 540px,
+    md: 720px,
+    lg: 960px,
+    xl: 1140px,
+    xxl: 1320px,
+);
+
+$grid-columns: 12;
+$grid-gutter-width: rem-calc(20px);
+$grid-row-columns: 6;