Tweaked Telegram configuration docs and added an explicit error on message failure

[v4dkou]

Added printing an explicit error in case of Telegram misconfiguration Amended sample_config.yaml to highlight a possible point of failure

Great project overall, just had to spend a significant amount of time figuring out why topics and messages were not mirroring correctly due to the error being silent

[akshettrj]

Thanks for the PR. What was the error finally?

[v4dkou]

@akshettrj The Telegram API was responding with "Bad Request: chat not found", because I've copied the chatId from Telegram Web as is without adding the "100" prefix of a supergroup