🔥 Feature: Add docker build options

[grivera64]

Feature Description

This PR adds an option to build AstraKernel using Docker. Users can simply run make docker to run the latest main branch version of docker (or make docker-dev to run their checked out local version of AstraKernel for development).

File Changes

• Add Dockerfile, Dockerfile.dev, and .dockerignore for Docker build support
• Add docker and docker-dev rules to Makefile
• Add docker build instructions to README.md

Feature Example

$ make docker
========================================
  AstraKernel  v0.1.0
  Built May 26 2025 at 06:05:04
========================================

  CPU: ARM926EJ-S @ 200MHz (simulated)
  RAM: 128MB SDRAM at 0x00000000

Welcome to your own little Astra world!
Type away, explore, have fun.

AstraKernel is running...
Press Ctrl-A and then X to exit QEMU.

AstraKernel > 

[chrisdedman]

LGTM

[chrisdedman]

Looks great. Thank you for your contribution :)