An ECONNRESET in npm means that npm is unable to connect to an URL where it's looking for dependencies or resources. In most cases, that means that your npm is unable to connect to the NPM Registry. But in your case it seems different.
You're trying to create a Stencil app, with npm init stencil. Under the hood, that That means you're using npm to download the create-stencil package and run it to generate the scaffold of your Stencil app.
The first part, getting the create-stencil package works well, the problem arrives while running the package. If I am correct, create-stencil tries to clone the stencil-app-starter GitHub repository and modify it. So maybe you're behind a corporate or university proxy, blocking GitHub, or another the URLs of the create-stencil resources, maybe the connection is rather flacky, maybe GitHub was done at that moment...