Dependencies from Docker image not found in the running container

Background

So I'm trying to set up a Docker container for development, and one of my dependencies is webpack.

Repo Steps:

1. install this in the image with an npm install webpack.
2. The image builds successfully
3. I run it
4. In the Docker Desktop GUI shell I type webpack -v
5. Then get output webpack: command not found.

Question

How does it not find the command if it was one of the dependencies installed on the base image?