DOC - Add development instructions

Add instructions for installing the package in development version

README.md

@@ -26,6 +26,84 @@ To remove the extension, execute:
 pip uninstall jupyterlab-conda-store
 ```
 
+## Installing the development version
+
+### Pre-requisites
+
+1. You will need to have [NodeJS](https://nodejs.org/en/download/) installed on your local computer to build the extension package.
+2. Python >= 3.8 and `pip`.
+
+### Building and linking the extension
+
+> **Note**
+> The `jlpm` command is JupyterLab's pinned version of [yarn](https://yarnpkg.com/) that is installed with JupyterLab. You may use`yarn` or `npm` in lieu of `jlpm` in the commands below.
+
+1. Clone this repository to your local computer:
+
+   ```bash
+   git clone https://github.com/conda-incubator/jupyterlab-conda-store.git
+   ```
+
+2. Change to the `jupyterlab-conda-store` directory:
+
+   ```bash
+    cd jupyterlab-conda-store
+   ```
+
+3. Optional but recommended - Create and activate a development environment with conda:
+
+   ```bash
+   # Create environment named `jupyterlab-conda-store`
+   conda create -n jupyterlab-conda-store
+   conda activate jupyterlab-conda-store
+   ```
+
+4. Install JupyterLab and NodeJS **if not installed**:
+
+   ```bash
+   # Install node and jupyterlab from conda-forge
+   conda install -c conda-forge 'nodejs>16' 'jupyterlab<4'
+   ```
+
+5. Install the package in development mode:
+
+   ```bash
+   pip install -e .
+   ```
+
+6. Now you'll need to link the development version of the extension to JupyterLab and rebuild the Typescript source:
+
+   ```bash
+   # Link your development version of the extension with JupyterLab
+   jupyter labextension develop . --overwrite
+   ```
+
+7. On the first installation, or after making some changes, to visualize them in your local JupyterLab re-run the following command:
+
+   ```bash
+   # Rebuild extension Typescript source after making changes
+   jlpm build
+   ```
+
+8. Run JupyterLab and check that the installation worked:
+
+```bash
+# Run JupyterLab
+jupyter lab
+```
+
+### Uninstalling the development version
+
+1. Remove the extension:
+
+   ```bash
+   pip uninstall jupyterlab-conda-store
+   ```
+
+2. In development mode, you will also need to remove the symlink created by `jupyter labextension develop`
+   command. To find its location, you can run `jupyter labextension list` to figure out where the `labextensions`
+   folder is located. Then you can remove the symlink named `jupyterlab-conda-store` within that folder.
+
 ## Release
 
 To create a new pacakge and release: