Improvements to README.md

[SimonVandeVyver]

Here are some small suggestions to improve the "Running as snakemake workflow" section in README.md:

• In the first step of the section , you can add to use conda --version and mamba --version to check the installation.
• I got the following error when running condo activate peptonizer: CondaError: Run 'conda init' before 'conda activate'. This error was fixed by running condo init and restarting the terminal.
• In the last step of the section "Running as snakemake workflow", it might be useful for the reader to know they will execute the peptonizer with the 'S03' dataset, as in the "Testing the peptonizer" section.