Improve the readme with contributing guidelines

Addresses issue https://github.com/microsoft/markitdown/issues/6

---

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README.md

@@ -37,6 +37,30 @@ This project has adopted the [Microsoft Open Source Code of Conduct](https://ope
 For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or
 contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
 
+## Installation
+
+To install the dependencies for this project, run the following command in the root of the project:
+
+```sh
+pip install -e .
+```
+
+## Running Tests
+
+To run the tests for this project, use the following command:
+
+```sh
+pytest
+```
+
+## Running Pre-commit Checks
+
+If there are pre-commit hooks configured (indicated by the `.pre-commit-config.yaml`), you can test them by running:
+
+```sh
+pre-commit run --all-files
+```
+
 ## Trademarks
 
 This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft