Feature: check_or_install talosctl

[TrooperT]

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