Update install-kubectl.md to use tabs for the different Operating Systems (#26682)

* top-level tags and change to included files

* revert content to main windows page

* include gcloud and update toc

* add leading blank line

* add text to avoid YAML error from Netlify

* remove YAML delimiter error

* removed redundant weight key

* add front matter and toc shortcode

* test to see if toc is fixed in included page

* update macos toc to show difference

* use static toc instead of shortcode

* uniqueness for gcloud install headers

* Move to model suggested in https://github.com/kubernetes/website/pull/26682#discussion_r585091797

* correct link to included/install-kubectl-gcloud.md

* correction of links to per-OS pages

* try a different way to use path to per-OS links

* correction of brainfart

* remove .md from link destination for per-OS pages

* modify how auto-competion steps are displayed

* remove redundant file

* correction of include - change % to <

* remove closing tag as not needed

* try and hide this directory from the ToC on the left

* remove erroneous "include="

* addressing feedback: https://github.com/kubernetes/website/pull/26682#discussion_r586325123

* addressing feedback: https://github.com/kubernetes/website/pull/26682#discussion_r586326346

* addressing feedback: https://github.com/kubernetes/website/pull/26682#discussion_r586326604

* addressing feedback: https://github.com/kubernetes/website/pull/26682#discussion_r586327212

* https://github.com/kubernetes/website/pull/26682#discussion_r586327856

* consistent verb usage as per feedback: https://github.com/kubernetes/website/pull/26682#discussion_r586328497

* update redirects as existing page is being deleted

content/en/docs/tasks/tools/included/install-kubectl-gcloud.md

@@ -0,0 +1,21 @@
+---
+title: "gcloud kubectl install"
+description: "How to install kubectl with gcloud snippet for inclusion in each OS-specific tab."
+headless: true
+---
+
+You can install kubectl as part of the Google Cloud SDK.
+
+1. Install the [Google Cloud SDK](https://cloud.google.com/sdk/).
+
+1. Run the `kubectl` installation command:
+
+   ```shell
+   gcloud components install kubectl
+   ```
+
+1. Test to ensure the version you installed is up-to-date:
+
+   ```shell
+   kubectl version --client
+   ```