Feature: check_or_install talosctl

Fixes #3 Adds a .gitignore for scratch directories at any depth

Add a reusable shell function with parameters to check for a binary, and prompt with corrective action if missing.

New filesystem paths used/created:

$HOME/.tbs/bin
- prepended to $PATH
- serves to store local-use copies of any downloaded binaries

New soft dependencies:

https://github.com/jpillora/installer
- generates a bash install script based on the needed binary, version, install behaviour, and includes OS/ARCH detection
- hosted at https://i.jpillora.com

aenix-io / talos-bootstrap