Pass raw information to the template

[adiroiban]

In https://github.com/hawkowl/towncrier/blob/9a71e71f8b08937439bbeb9c51922aba44feea3e/src/towncrier/_builder.py#L96 towncries tries to be useful and automatically adds a # to integer ticket numbers.

I think that this should be left to the template. For some systems like JIRA is common to not have a integer only id... and some people might want to use a different marker to highlight a ticket

thanks!