feat: make env variables accessible

[cfabianski]

Make Env Variables publicly accessible.

I used this new function to include the environment variables automatically in the doc Bearer/bearer#1446

[github-actions]

👋 Thanks for contributing to Viper! You are awesome! 🎉

A maintainer will take a look at your pull request shortly. 👀

In the meantime: We are working on Viper v2 and we would love to hear your thoughts about what you like or don't like about Viper, so we can improve or fix those issues.

⏰ If you have a couple minutes, please take some time and share your thoughts: https://forms.gle/R6faU74qPRPAzchZ9

📣 If you've already given us your feedback, you can still help by spreading the news,
either by sharing the above link or telling people about this on Twitter:

https://twitter.com/sagikazarmark/status/1306904078967074816

Thank you! ❤️

[fmontorsi-equinix]

I'd love to have this merged btw.
I think it would be so useful to provide automatic, always in-sync documentation about all environment variables being used by applications...