Add WireGuard Portal to VPN list in README

[kstieger]

Thank you for taking the time to work on a PR for Awesome-Sysadmin!

To ensure your PR is dealt with swiftly please check the following:

• Your additions are Free software
• Software you are submitting is not your own, unless you have a healthy ecosystem with a few contributors (which aren't your sock puppet accounts).
• Submit one item per pull request. This eases reviewing and speeds up inclusion.
• Format your submission as follows, where Demo and Clients are optional.
  Do not add a duplicate Source code link if it is the same as the main link.
  Keep the short description under 80 characters and use sentence case
  for it, even if the project's webpage or readme uses another capitalisation.
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  - [Name](http://homepage/) - Short description, under 250 characters, sentence case. ([Demo](http://url.to/demo), [Source Code](http://url.of/source/code), [Clients](https://url.to/list/of/related/clients-or-apps)) `License` `Language`
• Additions are inserted preserving alphabetical order.
• Additions are not already listed at awesome-selfhosted
• The Language tag is the main server-side requirement for the software. Don't include frameworks or specific dialects.
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• Any category you are creating has the minimum requirement of 3 items.
• Any software project you are adding to the list is actively maintained.
• The pull request title is informative, unlike "Update README.md".
  Suggested titles: "Add aaa to bbb" for adding software aaa to section bbb,
  "Remove aaa from bbb" for removing, "Fix license for aaa", etc.

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Please take some time to answer the following questions as best you can:

• Why is it awesome?

It is easy to setup and has a nice looking web admin interface. Docker deployment is up and running in a few minutes. It has also some advanced features like LDAP, OAuth, or OpenID.

• Have you used it? For how long?

We have been using it in the company for about 3 years.

• Is this in a personal or professional setup?

professional

• How many devices/users/services/... do you manage with it?

About 100 Accounts and up to 60 concurrent connections. Thanks to the low footprint it might handle much more ...

• Biggest pros/cons compared to other solutions?

  • Pro:
    • easy installation
    • hassle free configuration
    • good documentation, no blala, just the importtant facts
  • Con:
    • pushing routing changes to peer would be a nice additional feature
    • no MFA

• Any other comments about your use case, things you've found excellent, limitations you've encountered... ?
  see Cons. But no sho stopper. According to GitHub issues, the maintainer is very committed. Bugs are fixed quickly. They are also open to feature requests. (According to GitHub issues)