Updated the getting started file (#20)

Author: igarousi

GettingStarted.md

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+## Clone the repository
+Run the following command to clone the repository and navigate into it:
+
+    git clone https://github.com/hydroframe/cssi_evaluation.git
+
+    cd cssi_evaluation
+
+## Set up the recommended local environment
+
+Run these commands from the repository root. This assumes that conda and mamba are already installed (e.g., conda install mamba -n base -c conda-forge).
+
+    mamba env create -f cssi_env.yml
+
+    conda activate cssi_evaluation
+
+    python -m ipykernel install --user --name=cssi_evaluation
+
+The environment file installs the local `cssi_evaluation` package in editable mode with the
+`[notebooks,dev]` extras, so package imports, notebooks, and development tools are available in
+the same environment.
+
+## Notes
+
+- `pyproject.toml` is the package metadata file used by `pip install -e .`. It contains core library dependencies. 
+- `cssi_env.yml` is the single Conda environment file intended for running examples and it contains heavy Conday/system dependencies.