Documented openorca download recipe

dataset_openorca_mlperf_recipe/docs_axs.md

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+## Usage
+
+This recipe downloads the OpenOrca dataset used for Llama2-70b inference submissions
+
+### Command Anatomy
+Only run the 2nd producer rule.
+
+```bash
+axs byquery downloaded,dataset_name=openorca,
+            model_family=llama2, # The model family to use - Note more changes will need to be made for this to properly work with different model families. The reason for this is that the input column has llama2 specific tags, which must be converted.
+            variant=7b,
+            total_samples=24576 # The total number of samples to convert
+```
+### Misc
+Make sure you've downloaded the relevant tokeniser first.