i18n: add landing page translations (en/ru)

Added/updated translations for:
- howto: step labels
- stats: suppliers desc, countries
- testimonial: quote, author, role
- roles: subtitle, updated benefits
- cta: register, demo buttons
- footer: all countries, offices, products, services, legal

i18n/locales/en/stats.json

@@ -2,8 +2,10 @@
   "stats": {
     "title": "Optovia in Numbers",
     "suppliers": "Suppliers",
+    "suppliersDesc": "Verified producers from Russia, Kazakhstan and other CIS countries",
     "transactions": "Transaction Volume",
     "service_companies": "Service Companies",
-    "support": "Support"
+    "support": "Support",
+    "countries": "Countries of Presence"
   }
 }