docs: improve README wording and getting started instructions

[Samuel25-hub]

Description

I noticed a few small documentation issues in the README that could make the initial setup and contribution workflow clearer for new users and contributors.

Proposed improvements

1. Fix the wording:

   • Issue: The is a collection of attack data.
   • Should be: "This is a collection of attack data.

2. Standardize terminology:

   • Issue: "pre-requisite"
   • Should be: "prerequisite"

3. Improve capitalization and punctuation in the Getting Started instructions.

4. Clarify the distinction between the "Getting Started" and "Quick Start" sections so new contributors can more easily understand the setup and content-development workflow.

These would be documentation-only changes and would not modify any detection logic or security content.

I would be happy to submit a documentation PR addressing these items if this would be useful.

[Samuel25-hub]

While reviewing the README for the documentation improvements described above, I identified several additional grammar, punctuation, and clarity issues.

I would like to include these minor documentation corrections in the same PR, while keeping the scope limited to documentation and avoiding any changes to detection logic or functionality.

The additional fixes include wording, sentence structure, punctuation, and consistency improvements in the Getting Started, Quick Start, Recommendations, Content Parts, and related sections.