Improve documentation and fix install script URL

What does this PR do?

The lines in the ASCII art of README.md and BLOG.md have been aligned properly for improved readability. Additionally, the installer script in README.md, BLOG.md, CONTRIBUTING.md and install.sh have been fixed with the correct URL.

Type of change

• Bug fix
• New feature
• Performance improvement
• Documentation update
• Refactoring (no behavior change)

Testing

• Tested on x86-64 (Linux/macOS/Windows)
• Tested on ARM64 (Raspberry Pi)
• Tested with TinyLlama 1.1B Q4_K_M

Test command:

./picolm model.gguf -p "The capital of France is" -n 20 -t 0

Output:

Not needed

Checklist

• Code compiles without warnings (make native)
• No new dependencies added
• Memory usage not increased (check stderr output)
• Works with --json mode (if touching generation/sampling)