docs[minor]: lcel why page (#14089)

docs/src/theme/Columns.js

@@ -0,0 +1,17 @@
+import React from "react";
+
+export function ColumnContainer({children}) {
+    return (
+        <div style={{ display: "flex", flexWrap: "wrap" }}>
+            {children}
+        </div>
+    )
+}
+
+export function Column({children}) {
+    return (
+        <div style={{ flex: "1 0 300px", padding: "10px", overflowX: "clip" }}>
+            {children}
+        </div>
+    )
+}