Docs: Rename "Development" section to "Contributing" and add instructions to update the base AMI version of Ubuntu

docs/contributing/update_ami_versions.md

@@ -0,0 +1,16 @@
+# Updating The Default Base AMI
+
+With the release of `kOps 1.18`, the base AMI was switched over from a pre-baked `kOps` AMI to the official Ubuntu 20.04 LTS image.
+This makes the image update process easier, because kOps contributors no longer have to fully build and test a full AMI, but rather base off of the latest stable Ubuntu image.
+In order to make sure we're up to date with the latest releases, we regularly follow the official [Ubuntu EC2 AMI Locator](https://cloud-images.ubuntu.com/locator/ec2/) website and update to the latest version of `focal` which is available across **all AWS regions**, including `gov` and `cn`, for full support.
+
+The process of updating the AMI version is as following:
+
+- Find the most recent release on the official [Ubuntu EC2 AMI Locator](https://cloud-images.ubuntu.com/locator/ec2/). Make sure it's available across all regions. The ones with the slowest release cycle are usually `gov`, `ap` and `cn` ones, so the best option would usually be to take the most recent release from one of these regions.
+- Replace the timestamp on this line in the `alpha` channel, where the `ubuntu` image is referred. [Example](https://github.com/kubernetes/kops/blob/25eb1c98225450bed82d38e52d150d7a69a2c95a/channels/alpha#L47).
+
+    !!!note
+        Before updating `alpha` channel, check and see if `alpha` and `stable` channel are both running the same AMI version. If `stable` currently runs a different version, and more than 7-10 days passed since `alpha` was updated- it's safe to also push the version currently in `alpha`, to `stable` in the same PR.
+        e.g., let's say that the most recent available on Ubuntu image locator is `20201210`, `alpha` is currently using `20201101` and `stable` is currently using `20201015`. If `alpha` was updated at least 7-10 days prior to your desired change, you can update `stable` with the version that was listed in `alpha` **before** your change. Then- you may update `alpha` with the most recent version of Ubuntu.
+
+- Let the new AMI version bake-in in `alpha` channel for at least 7-10 days, afterwhich it's safe to create a follow-up PR to push the latest version to `stable` channel.  

mkdocs.yml

@@ -34,7 +34,6 @@ nav:
   - Welcome:
     - Welcome: "index.md"
     - Releases & Versioning: "welcome/releases.md"
-    - Contributing: "welcome/contributing.md"
     - Office Hours: "welcome/office_hours.md"
   - Getting Started:
     - Installing: "getting_started/install.md"
@@ -131,24 +130,27 @@ nav:
     - Rotate Secrets: "rotate-secrets.md"
     - Terraform: "terraform.md"
     - Authentication: "authentication.md"
-  - Development:
-    - Building: "development/building.md"
-    - Adding a feature: "development/adding_a_feature.md"
-    - Testing: "development/testing.md"
-    - New Kubernetes Version: "development/new_kubernetes_version.md"
-    - Developing using Docker: "development/Docker.md"
-    - Documentation Guidelines: "development/documentation.md"
-    - Hack Directory: "development/hack.md"
-    - How to update kOps API: "development/api_updates.md"
-    - Low level description on how kOps works: "development/how_it_works.md"
-    - Notes on Gossip design: "development/gossip.md"
-    - Notes on master instance sizing: "development/instancesizes.md"
-    - Our release process: "development/release.md"
-    - Releasing with Homebrew: "development/homebrew.md"
-    - Bazel: "development/bazel.md"
-    - Vendoring: "development/vendoring.md"
-    - Ports: "development/ports.md"
-    - Cluster Addons & Manager : "development/addons.md"
+  - Contributing:
+    - Getting Involved and Contributing: "contributing/contributing.md"
+    - New Kubernetes Version: "contributing/new_kubernetes_version.md"
+    - Our Release Process: "contributing/release.md"
+    - Releasing With Homebrew: "contributing/homebrew.md"
+    - Updating The Default Base AMI: "contributing/update_ami_versions.md"
+    - Development:
+      - Building: "contributing/development/building.md"
+      - Adding a feature: "contributing/development/adding_a_feature.md"
+      - Testing: "contributing/development/testing.md"
+      - Developing using Docker: "contributing/development/Docker.md"
+      - Documentation Guidelines: "contributing/development/documentation.md"
+      - Hack Directory: "contributing/development/hack.md"
+      - How to update kOps API: "contributing/development/api_updates.md"
+      - Low level description on how kOps works: "contributing/development/how_it_works.md"
+      - Notes on Gossip design: "contributing/development/gossip.md"
+      - Notes on master instance sizing: "contributing/development/instancesizes.md"
+      - Bazel: "contributing/development/bazel.md"
+      - Vendoring: "contributing/development/vendoring.md"
+      - Ports: "contributing/development/ports.md"
+      - Cluster Addons & Manager : "contributing/development/addons.md"
   - Releases:
     - "1.18": releases/1.18-NOTES.md
     - "1.17": releases/1.17-NOTES.md