Simplify sample template

[cdebost]

The straightforward bit:

• Removes .editorconfig, .gitignore, LICENSE.md, README.md files. Not necessary in a sample.

For review:

• Removes the assets/style/style.css from samples in favor of using the main app's stylesheet. I think it's much better to ensure some consistency in the global style rules and avoid surprises when moving from the sample to the actual app.
• Removes the assets/icons directory, using favicon.ico as the icon instead. Also removes said icons from the manifest file and removes some responsive web app tags from index.html. Based on my understanding, we'd only need these icons to make samples into progressive web apps, which I don't think there would ever be a reason for.

[tejaede]

Removes the assets/style/style.css from samples in favor of using the main app's stylesheet. I think it's much better to ensure some consistency in the global style rules and avoid surprises when moving from the sample to the actual app.

I agree that it's best to match the app's global style in the sample, but UI Kits don't have or need a global stylesheet so this results in a 404 and no global styles are applied. Maybe we can check for the existence of the main app stylesheet and only point to it if it exists? If not, I think it's better to leave it generic and make it the responsibility of the developer to match the sample styles to the app styles.