docs: update README to provide release install steps and remove dev/release workflows

[R4ULtv]

Motivation

• Replace developer-focused build and release instructions with simple end-user install steps for the release package.
• Remove outdated developer and publishing guidance and the tech stack list to streamline the README for users.

Description

• Updated README.md to add an "Install (Release)" section with step-by-step instructions for downloading the latest .zip release and loading it via chrome://extensions.
• Removed developer build instructions that referenced bun run build and loading the dist/ folder, and removed the previous "Releases" publish guide that included version/tagging examples and bash commands.
• Removed the prior "Stack" list and added a short post-install note instructing users to open YouTube to start using Paco.

Testing

• No automated tests were executed for this documentation-only change.

---

Codex Task