README enhancement request

[rajan-mis]

Describe the bug

I am opening this on behalf of another team outside of Scale that attempted to use the instructions and ran into issues with some of the wording. This was from someone that didn't know what an Self Extracting package was, so I think we can add a little statement somewhere explaining it or at least the naming convention to know when they have the actual SE package vs a tar file, etc.

The confusing part was here from: https://github.com/IBM/ibm-spectrum-scale-install-infra#installation-instructions

Create Ansible playbook
The basic Ansible playbook (e.g. ./playbook.yml) looks as follows:
# playbook.yml:
---
- hosts: cluster01
 vars:
   - scale_install_localpkg_path: /path/to/Spectrum_Scale_Standard-5.0.4.0-x86_64-Linux-install
 roles:
   - core/precheck
   - core/node
   - core/cluster
   - core/postcheck
Specifically: scale_install_localpkg_path

For someone unfamiliar with this, it's not super clear this is the full path including the SE package. At first, they pointed it to the .tar.gz file that was downloaded and then when that didn't work, they tried just pointing to the directory where the file was located which also didn't work. Once I explained what the SE package was, the format it was in, they were able to make progress by extracting it from the tar.gz and then pointing directly to it.

There is just a few additional details we can add to make it clearer to a customer who is not as familiar with the terminology.