postcss-simple-vars: Add media query breakpoint variables.

static/js/css_variables.js

@@ -0,0 +1,24 @@
+"use strict";
+
+// Media query breakpoints according to Bootstrap 4.5
+const xs = 0;
+const sm = 576;
+const md = 768;
+const lg = 992;
+const xl = 1200;
+
+module.exports = {
+    media_breakpoints: {
+        "xs-min": xs + "px",
+        "sm-min": sm + "px",
+        "md-min": md + "px",
+        "lg-min": lg + "px",
+        "xl-min": xl + "px",
+
+        "xs-max": xs - 1 + "px",
+        "sm-max": sm - 1 + "px",
+        "md-max": md - 1 + "px",
+        "lg-max": lg - 1 + "px",
+        "xl-max": xl - 1 + "px",
+    },
+};