Add GatewayD

[mostafa]

We want to ensure high quality of the packages. Make sure that you've checked the boxes below before sending a pull request.

• [x] I have read the Contribution Guidelines
• [x] I have read the Maintainers Note
• [x] I have read the Quality Standards

Not every repository (project) will require every option, but most projects should. Check the Contribution Guidelines for details.

• [x] The repo documentation has a pkg.go.dev link.
• [x] The repo documentation has a coverage service link.
• [x] The repo documentation has a goreportcard link.
• [x] The repo has a version-numbered release and a go.mod file.
• [x] The repo has a continuous integration process that automatically runs tests that must pass before new pull requests are merged.
• [x] Continuous integration is used to attempt to catch issues prior to releasing this package to end-users.

Please provide some links to your package to ease the review

• [x] forge link (github.com, gitlab.com, etc): https://github.com/gatewayd-io/gatewayd
• [x] pkg.go.dev: https://pkg.go.dev/github.com/gatewayd-io/gatewayd
• [x] goreportcard.com: https://goreportcard.com/report/github.com/gatewayd-io/gatewayd
• [x] coverage service link (codecov, coveralls, etc.): https://coveralls.io/github/gatewayd-io/gatewayd?branch=main

Pull Request content

• [x] The package has been added to the list in alphabetical order.
• [x] The package has an appropriate description with correct grammar.
• [x] As far as I know, the package has not been listed here before.

Category quality

Note that new categories can be added only when there are 3 packages or more.

Packages added a long time ago might not meet the current guidelines anymore. It would be very helpful if you could check 3-5 packages above and below your submission to ensure that they also still meet the Quality Standards.

Please delete one of the following lines:

• [x] The packages around my addition still meet the Quality Standards.

Thanks for your PR, you're awesome! :sunglasses: