Add .devcontainer to standardize environment and automate repo setup

[mattmazzola]

Issue

The setup for GPT4RoI repo is complicated and can become a large barrier for others to contribute.

Solution

Use .devcontainer to standardize development environment and automate installation steps

Automates (see .devcontainer/postCreateCommand.sh)

• Guarantees correct versions of python, cuda, cuda compiler and torch to allow building the packages using native C++ compilation such as flash-attn and mmcv
• Installation of root package
• Downloading of pretrained models llama-7b-hf and GPT4RoI-7B-delta-V0 and run script to apply delta
• Installation of NVM, install node, install pnpm, clone gradio-box, and build package for usage in demo

Video

I likely won't be able to work more on this, but I thought it could be useful for others.