feat: add CI and Codecov badges to README and set up Codecov integration (#37)

* feat: add CI and Codecov badges to README

* fix: update Codecov badge to include authentication token

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Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: jamesbhobbs

README.md

@@ -1,5 +1,8 @@
 # Deepnote Extension for Visual Studio Code
 
+[![CI](https://github.com/deepnote/vscode-deepnote/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/deepnote/vscode-deepnote/actions/workflows/ci.yml)
+[![codecov](https://codecov.io/gh/deepnote/vscode-deepnote/graph/badge.svg?token=NH066XG7JC)](https://codecov.io/gh/deepnote/vscode-deepnote)
+
 A [Visual Studio Code](https://code.visualstudio.com/) extension that provides support for [Deepnote notebooks](https://deepnote.com/) directly within VS Code. This extension allows you to work with Deepnote notebooks in VS Code, bringing the rich data science capabilities of Deepnote to your favorite editor.
 
 ![Deepnote Projects](./images/deepnote-projects.png)