TL-81 make tr() function available within marketing website

Worse case: string will be double-localized. For example:
you have 2 phrases for spanish dictionary:
```{
"Sand": "Arena",
"Arena": "Plaza"
}```
so window.optly.tr("Sand") will be "arena" (correct - spanish for "sand") but if double translation will happen - window.optly.tr(window.optly.tr("Sand")) results to "Plaza" which is incorrect.