Add devcontainer.json to ease local dev environment setup

[Trigtrig]

Description

Adding a Dev Container configuration to ease local dev environment setup.

Motivation and Context

I recently contributed to the Selenium project for the first time (see #13583). I opted for the Dev Container variant to set up my local dev environment. This worked very well, but I had to create my own devcontainer.json to be able to work with my IDE and Dev Container. To make it easier to get started, especially for first time contributors, I would like to add a devcontainer.json to the Selenium project. This minimal devcontainer.json has two advantages:

1. IDEs will recognize that Dev Containers are supported when opening the project and may offer to create the container. Here is an example from Visual Studio Code:
   

2. contributors who do not have much knowledge of Dev Containers can use the devcontainer.json and the documentation link it contains as a starting point for their local dev environment.

According to the Dev Container documentation, I have placed the file in the preferred folder .devcontainer. Both IntelliJ IDEA and Visual Studio Code recognize this Dev Container configuration correctly.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[diemol]

Thank you, @Trigtrig!

Could you please add a simple note about this in the README file?

[diemol]

Wait, but now you are replacing the content. Someone might want to use the Dockerfile. Can you please leave your added content and merge it with what already exists?

[Trigtrig]

My bad. I thought that the main purpose of the Docker image was to create a Dev Container. I restored the original section.

[diemol]

Thank you, @Trigtrig!