migrate site content: contributing docs (#4709)

* migrate contributing docs

* modifies weight for ordering

* updates links and info based on feedback

* removes broken powershell link

* Update site/content/en/contribute/windows/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

* Update site/content/en/contribute/windows/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

* Update site/content/en/contribute/mac/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

* Update site/content/en/contribute/howitworks/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

* Update site/content/en/contribute/howitworks/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

* simplify build explanation

* removes windows docs

* removes community - duplicate

* update the tooling instructions

* point to proposal docs

* Update site/content/en/contribute/howitworks/_index.md

Co-authored-by: Katrina Verey <kn.verey@gmail.com>

site/content/en/contribute/bugs/_index.md

@@ -0,0 +1,57 @@
+---
+title: "Filing Bugs"
+linkTitle: "Filing Bugs"
+type: docs
+weight: 10
+description: >
+    How to file bugs and fix Kustomize bugs
+---
+
+[krusty package]: https://github.com/kubernetes-sigs/kustomize/tree/master/api/krusty
+[reusable custom transformer test]: https://github.com/kubernetes-sigs/kustomize/tree/master/api/krusty/customconfigreusable_test.go
+[example PR]: https://github.com/kubernetes-sigs/kustomize/pull/4683
+
+File [issues](https://github.com/kubernetes-sigs/kustomize/issues) as desired, but if you've found a problem
+with how `kustomize build` works, please report:
+
+* the output of `kustomize version`,
+* the input (the content of `kustomization.yaml`
+   and any files it refers to),
+* the expected YAML output.
+
+## If you have `go` installed
+
+kustomize has a simple test harness in the [krusty
+package] for specifying a kustomization's input and the
+expected output.
+
+Copy one of those tests, e.g. this [reusable custom
+transformer test], to a new test file in the
+krusty package.
+
+Insert the inputs you want to use, and run it as
+you'd run the reusable custom transformer test:
+
+```
+(cd api; go test -run TestReusableCustomTransformers ./krusty)
+```
+
+The output will demonstrate the bug or missing feature.
+
+Record this output in the test file in a call to
+`AssertActualEqualsExpected`, per all the other tests
+in the [krusty package].  This makes the test pass,
+albeit with output demonstrating behavior you
+presumably want to change.
+
+Send the new test in a PR, along with commentary (in
+the test) on what you'd prefer to see. You can refer to this [example PR]
+
+The person who fixes the bug then has a clear bug
+reproduction and a test to modify when the bug is
+fixed.
+
+Any bug fix first requires a test demonstrating the bug
+(so we have permanent regression coverage), so if the
+_bug reporter_ does this, it saves time and avoids
+misunderstandings.