Create a GH checklist template for conformance tests

[carlisia]

These tests are reimplementation of the same conformance tests in https://github.com/knative/networking/tree/main/test/conformance/ingress. These tests are run without the net-gateway-api controller.

(test/kind-conformance-contour.sh)

With this checklist, a new issue can be opened for each implementation and each test checked off as the tests are confirmed as passing.

For visibility, maybe it would be useful to keep these issues pinned and check the tests on/off as the status of each changes.

These are all the tests: #348