ZCU-PUB/Added missing theme by string in cs.json5 (#925)

Author: jr-rk

src/assets/i18n/cs.json5

@@ -2160,6 +2160,8 @@
   "footer.link.contact-us": "Kontaktujte nás",
   // "footer.link.university": "University Library",
   "footer.link.university": "Univerzitni Knihovna",
+  // "footer.theme.by.message": "Theme by",
+  "footer.theme.by.message": "Theme by",
   // "forgot-email.form.header": "Forgot Password",
   "forgot-email.form.header": "Zapomenuté heslo",
   // "forgot-email.form.info": "Enter the email address associated with the account.",