updating contrib for ref docs (#18787)

more cleanup

content/en/docs/contribute/generate-ref-docs/prerequisites-ref-docs.md

@@ -0,0 +1,21 @@
+
+### Requirements:
+
+- You need a machine that is running Linux or macOS.
+
+- You need to have these tools installed:
+
+  - [Python](https://www.python.org/downloads/) v3.7.x
+  - [Git](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
+  - [Golang](https://golang.org/doc/install) version 1.13+
+  - [Pip](https://pypi.org/project/pip/) used to install PyYAML
+  - [PyYAML](https://pyyaml.org/) v5.1.2
+  - [make](https://www.gnu.org/software/make/)
+  - [gcc compiler/linker](https://gcc.gnu.org/)
+  - [Docker](https://docs.docker.com/engine/installation/) (Required only for `kubectl` command reference)
+
+- Your `PATH` environment variable must include the required build tools, such as the `Go` binary and `python`.
+
+- You need to know how to create a pull request to a GitHub repository.
+  This involves creating your own fork of the repository. For more
+  information, see [Work from a local clone](/docs/contribute/intermediate/#work_from_a_local_clone).