Add support for a new token type: regex

[celluj34]

Hello! This is the new issue for the feature I requested from #67.

I'd like to request a feature, to be able to select tokens using a regex pattern. It would probably require a new option, 'tokenPattern', instead of re-using the prefix or suffix options.

Please let me know if you need anything else.

[qetza]

Hi @celluj34,
I'm was looking at this request and couldn't find an example of a custom regex that couldn't be managed with custom token prefix and suffix. Could you share some example of regex you have in mind?

[celluj34]

Sure, basically I have an app that uses webpack to compile, and the config.json file needs to be transformed during deployment so that it can hold env-specific values. I need these files to be able to be transformed by bash's envsubst function, and it uses the syntax of $variableName. It uses a prefix but no suffix.

Some variables don't need to be transformed during each env separately, so I want to use this task to read my azure devops variables and replace the ones it can in the file.

Hopefully that makes sense, let me know if you need any more info!

nb: I've since moved on to having all of the variables transformed by bash inside the docker image, so I don't necessairly need this feature, but I thought it might be helpful for others.