Enable fallback if no translation exists for current tag.

[B1Z0N]

How do you think, do we need something like this?
Please see my gitpod changes in here(last commit via git diff HEAD HEAD^).

Posting it here because i'm not sure, but already had implemented the change. If reply is positive i'll open the PR.

[EdJoPaTo]

Are you seeking for defaultLanguageOnMissing or allowMissing?

Also you probably want to use https://github.com/grammyjs/i18n as this repo is unmaintained. It works with both grammY and Telegraf.