update pistinstall filepath and readme instructions

[petermsouzajr]

Description

I modified the postinstall script to be compatible with more systems. I updated the Readme with new phrasing and new instructions.

Type of change

• Bug fix
• Documentation update
• Code Refactor

Related Tickets & Documents

#103

How Has This Been Tested?

• This was tested on a local environment

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings, run: npm test
• My changes generate no new lint errors, run: npm run lint
• Fix auto-fixable linting errors by running npm run lint:fix
• Fix all other lint errors manually
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes, run: npm test