feat: add Docker support with multi-stage build

[AdityasWorks]

Overview

This PR adds Docker support to make it easy for anyone to build and run JSIR without dealing with complex local setup. It addresses issue #29

What's Included

Dockerfile
The Dockerfile uses a two-stage build approach to keep the final image size reasonable. The builder stage image is around 4.7GB and the final image is 190MB and takes about 7-8 minutes to build.

.dockerignore
Added to optimize the build context by excluding unnecessary files, which keeps the image lean and speeds up builds.

README.md Updates
Added a Docker quick start section as the recommended way to get started, with example commands for building and running.

Quick Start

Build the image

docker build -t jsir:latest .

Run jsir_gen

docker run --rm jsir:latest jsir_gen --help

Analyze a JavaScript file

docker run --rm -v $(pwd):/workspace jsir:latest \
  jsir_gen --input_file=/workspace/yourfile.js --passes=source2ast,ast2hir

Testing

I've verified that:

• Build completes successfully in 7-8 minutes
• jsir_gen --help works correctly
• /examples directory is included with test files
• Volume mounting for local file processing works as expected
• Output redirection to files works properly
• Ubuntu 24.04 runtime is 190MB (Debian bookworm-slim was tested at 193MB, 3MB larger)

Notes

The compiler warnings you'll see during build are expected (they're about C++20 extensions in C++17 mode) and don't indicate any problems. No source code modifications were needed.