Mention installing promptsource from source

Author: tridao

README.md

@@ -105,7 +105,8 @@ library.
 
 1. Pull the `lm-evaluation-harness` repo by `git submodule update --init
    --recursive`. We use the `big-refactor` branch.
-2. Install `lm-evaluation-harness`: `pip install -e 3rdparty/lm-evaluation-harness`
+2. Install `lm-evaluation-harness`: `pip install -e 3rdparty/lm-evaluation-harness`.
+On Python 3.10 you might need to manually install the latest version of `promptsource`: `pip install git+https://github.com/bigscience-workshop/promptsource.git`.
 3. Run evaluation with (more documentation at the [lm-evaluation-harness](https://github.com/EleutherAI/lm-evaluation-harness/tree/big-refactor) repo):
 ```
 python evals/lm_harness_eval.py --model mamba --model_args pretrained=state-spaces/mamba-130m --tasks lambada_openai,hellaswag,piqa,arc_easy,arc_challenge,winogrande --device cuda --batch_size 64