feat: add /trainings page

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

lib/currency/formatter.ts

@@ -0,0 +1,9 @@
+export function formatCurrency(price: number | bigint, locale: string = 'en-US', currency: string = 'CZK'): string {
+  const currencyFormatter = new Intl.NumberFormat(locale, {
+    style: 'currency',
+    currency: currency,
+    maximumFractionDigits: 0,
+  });
+
+  return currencyFormatter.format(price).replace(',', ' ')
+}