feat: add /trainings page

- list of trainings
- add button (taken from github: vojtechmares/website)
- add currency formatter

src/components/Button.tsx

@@ -0,0 +1,78 @@
+import Link from "next/link";
+import { ReactNode } from "react";
+
+function classNames(...classes: any) {
+  return classes.filter(Boolean).join(' ')
+}
+
+const baseStyles = {
+  solid:
+    "group inline-flex items-center justify-center rounded-md font-semibold focus:outline-none focus-visible:outline-2 focus-visible:outline-offset-2",
+  outline:
+    "group inline-flex ring-1 items-center justify-center rounded-md focus:outline-none",
+};
+
+const variantStyles = {
+  solid: {
+    black:
+      "bg-black text-white hover:bg-gray-700 active:bg-gray-800 focus-visible:outline-gray-900",
+    amber:
+      "bg-amber-500 text-white hover:bg-amber-600 active:bg-amber-800 focus-visible:outline-amber-500",
+    white:
+      "bg-white text-black hover:bg-amber-50 active:bg-amber-200 focus-visible:outline-white",
+  },
+  outline: {
+    black:
+      "ring-gray-200 text-black hover:ring-gray-300 active:bg-gray-100 focus-visible:outline-amber-500 focus-visible:ring-gray-300",
+    white:
+      "ring-gray-700 text-white hover:ring-gray-500 active:ring-gray-700 focus-visible:outline-white",
+    amber: "", // Outline buttons cannot be amber
+  },
+};
+
+const transitionStyle = "transition duration-150 ease-in-out";
+
+const sizeStyles = {
+  medium: "px-4 py-2 text-sm",
+  large: "px-8 py-4 text-base",
+};
+
+type Props = {
+  variant?: "solid" | "outline";
+  color?: "black" | "white" | "amber";
+  size?: "medium" | "large";
+  className?: string;
+  href?: string;
+  children?: ReactNode;
+};
+
+export function Button({
+  variant = "solid",
+  color = "black",
+  size = "medium",
+  className,
+  href,
+  children,
+}: Props) {
+  if (variant === "outline" && color === "amber") {
+    throw new Error("Outline buttons cannot be amber");
+  }
+
+  className = classNames(
+    baseStyles[variant],
+    variantStyles[variant][color],
+    sizeStyles[size],
+    transitionStyle,
+    className
+  );
+
+  if (href !== undefined) {
+    return (
+      <Link href={href} className={className}>
+        {children}
+      </Link>
+    );
+  } else {
+    return <button className={className}>{children}</button>;
+  }
+}