docs: update README based on feedback

Author: oli-hivemq

README.md

@@ -95,11 +95,16 @@ You added this library as a dependency to your repository's package.json.
   - Choose `Generate new token (classic)`.
   - In the scope, select at least `read:packages`.
   - Remember to copy the generated token before it disappears.
-1. Add the following line to your `.npmrc` file:
-  ```
-  //npm.pkg.github.com/:_authToken=your_new_token
+2. Save your new token to an environment variable (e.g. in `~/.bashrc` or `~/.zshrc`):
+```bash
+export NPM_TOKEN=${YOUR_TOKEN}
+```
+where `YOUR_TOKEN` is the token you obtained from Github remember to refresh your terminal after adding the it. (e.g. `source ~/.bashrc` depending on your shell)
+3. Add the following line to your `.npmrc` file:
+  ```bash
+  //npm.pkg.github.com/:_authToken=${NPM_TOKEN}
   ```
-1. Re-run your repository's installation step (e.g. `yarn install`).
+4. Re-run your repository's installation step (e.g. `yarn install`).
 
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