Add a shortcut for markitdown

Once we have set up the markitdown environment, we can quickly start it by defining a markitdown-init function in the .zshrc or .bashrc file.

# ~/.zshrc / ~/.bashrc
# markitdown (Microsoft) Settings
markitdown-init() {
    if conda info --envs | grep -q "markitdown"; then
        conda activate markitdown
	markitdown --version
    else
        echo "The Conda environment 'markitdown' does not exist. Please build 'https://github.com/microsoft/markitdown.git' first."
    fi
}

The requested entry points are ~/.zshrc and ~/.bashrc; start by checking the setup and usage instructions for how the markitdown Conda environment and CLI are launched. Add the markitdown-init shortcut with the requested missing-environment message and version check, then verify it in a shell with and without the markitdown environment.