🏃 added demo script

Add demo script to run quick demo of Kubebuilder. This is
also useful for recording demo videos using asciinema.

scripts/demo/README.md

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+This directory contains scripts to run a quick demo of KubeBuilder.
+
+Steps to run demo:
+
+```sh
+mkdir /tmp/kb-demo
+cd /tmp/kb-demo
+DEMO_AUTO_RUN=1 ./run.sh
+
+```

scripts/demo/run.sh

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+#!/bin/bash
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+clear
+. $(dirname ${BASH_SOURCE})/util.sh
+
+desc "Initialize Go modules"
+run "go mod init demo.kubebuilder.io"
+
+desc "Let's initialize the project"
+run "kubebuilder init --domain tutorial.kubebuilder.io"
+clear
+
+desc "Examine scaffolded files..."
+run "tree ."
+clear
+
+desc "Let's create cronjob api"
+run "kubebuilder create api --group batch --version v1 --kind CronJob"
+clear
+
+desc "Let's take a look at the API and Controller files"
+run "tree ./api ./controllers"
+clear
+
+desc "Install CRD in Kubernetes cluster"
+run "make install"
+clear
+
+desc "Run controller manager locally"
+run "make run"

scripts/demo/util.sh

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+#!/bin/bash
+# Copyright 2016 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file is copied from @thockin's micro-demos repository:
+# https://github.com/thockin/micro-demos/blob/master/util.sh
+
+readonly  reset=$(tput sgr0)
+readonly  green=$(tput bold; tput setaf 2)
+readonly yellow=$(tput bold; tput setaf 3)
+readonly   blue=$(tput bold; tput setaf 6)
+readonly timeout=$(if [ "$(uname)" == "Darwin" ]; then echo "1"; else echo "0.1"; fi) 
+
+function desc() {
+    maybe_first_prompt
+    rate=25
+    if [ -n "$DEMO_RUN_FAST" ]; then
+      rate=1000
+    fi
+    echo "$blue# $@$reset" | pv -qL $rate
+    prompt
+}
+
+function prompt() {
+    echo -n "$yellow\$ $reset"
+}
+
+started=""
+function maybe_first_prompt() {
+    if [ -z "$started" ]; then
+        prompt
+        started=true
+    fi
+}
+
+# After a `run` this variable will hold the stdout of the command that was run.
+# If the command was interactive, this will likely be garbage.
+DEMO_RUN_STDOUT=""
+
+function run() {
+    maybe_first_prompt
+    rate=25
+    if [ -n "$DEMO_RUN_FAST" ]; then
+      rate=1000
+    fi
+    echo "$green$1$reset" | pv -qL $rate
+    if [ -n "$DEMO_RUN_FAST" ]; then
+      sleep 0.5
+    fi
+    OFILE="$(mktemp -t $(basename $0).XXXXXX)"
+    if [ "$(uname)" == "Darwin" ]; then
+       script -q "$OFILE" $1
+    else
+       script -eq -c "$1" -f "$OFILE"
+    fi
+    r=$?
+    read -d '' -t "${timeout}" -n 10000 # clear stdin
+    prompt
+    if [ -z "$DEMO_AUTO_RUN" ]; then
+      read -s
+    fi
+    DEMO_RUN_STDOUT="$(tail -n +2 $OFILE | sed 's/\r//g')"
+    return $r
+}
+
+function relative() {
+    for arg; do
+        echo "$(realpath $(dirname $(which $0)))/$arg" | sed "s|$(realpath $(pwd))|.|"
+    done
+}
+
+trap "echo" EXIT