Update Environment.php

[filerun]

Added slug delimiter config. I needed slugs to use underscores instead of dashes. I could have extended the SlugNormalizer to do a str_replace as a quick solution for my needs, but the class is final. The library could use this option. (I edited the files in the browser, hence the patches rather than a single pull request. I hope it is going to be useful to somebody.)

[colinodell]

Thanks for proposing this change!

I'm in favor of including this functionality, but this will need a few more changes before it's ready for review and merge:

• Combine all of the PRs into a single PR
• Add tests proving the new feature works
• Update the documentation so users know the option is available

Would you be interest in making those changes within a single PR?

For now, I'll close the other PRs (#1091, #1092, and #1094) to keep this repo clean. Feel free to update this PR or create a new one with the combined changes.