Add an install script

Setup a simple install script (`install.sh`) that would download the required scripts to the user's local machine.

This could be inspired from the way that tools like pyenv [handle installs](https://realpython.com/intro-to-pyenv/#using-the-pyenv-installer) with their own install scripts. Ideally the user should be able to run something like the following to fetch the required scripts:
```
curl | bash
```

Start by inspecting the repository's existing shell scripts and the pyenv installer example linked in the issue. Add install.sh so a user can run the shown curl-to-bash command to download the required scripts locally, then verify the fetched scripts are available for use.

Written by the indexing model from the issue text.