Add Install tools script

[askmeegs]

No description provided.

[NimJay]

This issue was created as a result of some friction I logged in go/nimjay-friction-log-intro-to-krm-1:

The second biggest point of friction was the large number of tools that needed to be installed.

In my case, I had to install 6 new tools:

• kubectx
• Homebrew
• tree
• skaffold
• Cloud Code extension
• terraform

But I want to highlight that I am a very special case because I am new to the K8 world (and I'm even new to macOS).
I'm guessing most users of this tutorials will not have my problem. :)

I also want to mention that I like having control over how and what tools are installed on my machine — so a script that automatically installs a bunch of tools might not desirable.
Maybe a script that simply tells me which tools I still need to install (but doesn't actually install them for me) would be better.