Re-introduce welcome page to devfile starter

[scottkurz]

As we work in the devfile ecosystem it seems the strictly minimal starter, "don't include any code that will get deleted" may be causing trouble.

To balance the use cases of

• using the starter as a new java-openliberty and/or new devfile/odo/whatever-tooling user
• using the starter to actually create a new project (for productive work)

maybe we should add back in the welcome index.html.

I'm not sure this will even be the final word on the subject... but it'll get us to the next time we reconsider this.

[scottkurz]

Done in: https://github.com/OpenLiberty/application-stack-starters/pull/9