Ensure a single leading @ for twitter usernames

[samtrion]

This prevents destroying the template due to the incorrect use of quotes.

[ashmaroli]

Did you know?

Liquid also has a remove filter that seems to be more appropriate than replace in this use-case.

[samtrion]

I did not know. However, I have taken the Replace from the previous version.

[ashmaroli]

I understand that. But since the lines are being updated, its always best to use the most apt route.

[samtrion]

Done

[ashmaroli]

Thanks for updating. Do you by any chance know if @ is allowed after the first char? (e.g. @zombie@)

[samtrion]

Sorry, as far as I know the first @ is required, but if additional @ are allowed, I don't know

[samtrion]

https://help.twitter.com/en/managing-your-account/twitter-username-rules

It's not allowed:

A username can only contain alphanumeric characters (letters A-Z, numbers 0-9) with the exception of underscores...

[ashmaroli]

To avoid unnecessary String allocations.. (Certain Liquid filters duplicate the input string before processing it.)

[samtrion]

Done

[parkr]

A test could be helpful so we don't regress in the future!

[DirtyF]

@jekyllbot: merge +minor