Add option to get latest kubectl stable version and README to describe building local Docker image

Signed-off-by: Eldad Assis <eldada@jfrog.com>

Dockerfile

@@ -1,4 +1,6 @@
-# Build...
+# -----------------------------------------------------------------------------
+# The base image for building the k9s binary
+
 FROM golang:1.15.2-alpine3.12 AS build
 
 WORKDIR /k9s
@@ -8,15 +10,15 @@ COPY cmd cmd
 RUN apk --no-cache add make git gcc libc-dev curl && make build
 
 # -----------------------------------------------------------------------------
-# Build Image...
+# Build the final Docker image
 
 FROM alpine:3.12.0
+ARG KUBECTL_VERSION="v1.18.2"
 
 COPY --from=build /k9s/execs/k9s /bin/k9s
-ENV KUBE_LATEST_VERSION="v1.18.2"
 RUN apk add --update ca-certificates \
   && apk add --update -t deps curl vim \
-  && curl -L https://storage.googleapis.com/kubernetes-release/release/${KUBE_LATEST_VERSION}/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl \
+  && curl -L https://storage.googleapis.com/kubernetes-release/release/${KUBECTL_VERSION}/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl \
   && chmod +x /usr/local/bin/kubectl \
   && apk del --purge deps \
   && rm /var/cache/apk/*

Makefile

@@ -22,6 +22,9 @@ build:  ## Builds the CLI
 	-ldflags "-w -s -X ${PACKAGE}/cmd.version=${VERSION} -X ${PACKAGE}/cmd.commit=${GIT} -X ${PACKAGE}/cmd.date=${DATE}" \
 	-a -tags netgo -o execs/${NAME} main.go
 
+kubectl-stable-version:  ## Get kubectl latest stable version
+	@curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt
+
 img:    ## Build Docker Image
 	@docker build --rm -t ${IMAGE} .
 

README.md

@@ -1,4 +1,4 @@
-<img src="assets/k9s.png">
+<img src="assets/k9s.png" alt="k9s">
 
 # K9s - Kubernetes CLI To Manage Your Clusters In Style!
 
@@ -99,6 +99,8 @@ K9s is available on Linux, macOS and Windows platforms.
 
 ## Running with Docker
 
+### Running the official Docker image
+
   You can run k9s as a Docker container by mounting your `KUBECONFIG`:
 
   ```shell
@@ -111,6 +113,28 @@ K9s is available on Linux, macOS and Windows platforms.
   docker run --rm -it -v ~/.kube/config:/root/.kube/config quay.io/derailed/k9s
   ```
 
+### Building your own Docker image
+
+  You can build your own Docker image of k9s from the [Dockerfile](Dockerfile) with the following:
+
+  ```shell
+  docker build -t k9s-docker:0.1 .
+  ```
+
+  You can get the latest stable `kubectl` version and pass it to the `docker build` command with the `--build-arg` option.
+  You can use the `--build-arg` option to pass any valid `kubectl` version (like `v1.18.0` or `v1.19.1`).
+
+  ```shell
+  KUBECTL_VERSION=$(make kubectl-stable-version 2>/dev/null)
+  docker build --build-arg KUBECTL_VERSION=${KUBECTL_VERSION} -t k9s-docker:0.1 .
+  ```
+
+  Run your container:
+
+  ```shell
+  docker run --rm -it -v ~/.kube/config:/root/.kube/config k9s-docker:0.1
+  ```
+
 ---
 
 ## PreFlight Checks
@@ -630,7 +654,7 @@ roleRef:
 
 Example: Dracula Skin ;)
 
-<img src="assets/skins/dracula.png">
+<img src="assets/skins/dracula.png" alt="Dracula Skin">
 
 You can style K9s based on your own sense of look and style. Skins are YAML files, that enable a user to change the K9s presentation layer. K9s skins are loaded from `$HOME/.k9s/skin.yml`. If a skin file is detected then the skin would be loaded if not the current stock skin remains in effect.
 
@@ -736,9 +760,9 @@ to make this project a reality!
 ## Meet The Core Team!
 
 * [Fernand Galiana](https://github.com/derailed)
-  * <img src="assets/mail.png" width="16" height="auto"/>  fernand@imhotep.io
+  * <img src="assets/mail.png" width="16" height="auto" alt="email"/>  fernand@imhotep.io
-  * <img src="assets/twitter.png" width="16" height="auto"/> [@kitesurfer](https://twitter.com/kitesurfer?lang=en)
+  * <img src="assets/twitter.png" width="16" height="auto" alt="twitter"/> [@kitesurfer](https://twitter.com/kitesurfer?lang=en)
 We always enjoy hearing from folks who benefit from our work.
 ---
 
-<img src="assets/imhotep_logo.png" width="32" height="auto"/> &nbsp;© 2020 Imhotep Software LLC. All materials licensed under [Apache v2.0](http://www.apache.org/licenses/LICENSE-2.0)
+<img src="assets/imhotep_logo.png" width="32" height="auto" alt="Imhotep"/> &nbsp;© 2020 Imhotep Software LLC. All materials licensed under [Apache v2.0](http://www.apache.org/licenses/LICENSE-2.0)