[DOCUMENTATION] Explain custom packages system

[youngcoder45]

Document how packages are built and managed.

Context:
Repo includes pkgbuild/ and repo/ but lacks explanation.

Suggested approach:

1. Study folder structure
2. Write docs/PACKAGES.md
3. Explain:
   • PKGBUILD
   • repo structure

Acceptance criteria:

• Clear explanation of package workflow

Files:

• pkgbuild/
• repo/