Installation instructions updated

[bralat]

This pull request contains fixes for minor issues I encountered while trying to use this software:

1. The repository link in the instructions, git clone https://github.com/clic-lab/instruction-following-framework.git, no longer exists.
2. The prefix in the command python3 src/experiment_domain_name/experiment_name.py was experiment but the folder uses the plural form experiments

With this pull request, the following changes are made:

1. Repo link in read me is updated to git clone https://github.com/lil-lab/ciff.git
2. Prefix for domain name in read me changed from experiment to experiments to match folder names