Update loop unroll readme.md

[jkinsky]

Existing Sample Changes

Description

Restructured readme to match new template. Updated branding. Rewrote for clarity and added some Windows information.

Fixes Issue#

External Dependencies

N/A

Type of change

Please delete options that are not relevant. Add a 'X' to the one that is applicable.

• [X] Documentation

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Command Line
• [x] oneapi-cli
• [x] Visual Studio
• [x] VSCode

[jkinsky]

@ishaghosh27 please review. Adding @jimmytwei for notifications.