Create readme.md

Creating a readme which outlines the content here for the CLI

Author: jpe316

cli/readme.md

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+# CLI Example Content
+This content can be used in conjunction with our [CLI reference guide.](https://docs.microsoft.com/en-us/azure/machine-learning/service/reference-azure-machine-learning-cli)
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+Example content includes training scripts, conda environment files and scoring files.