copy NOTICE file in addition to LICENSE file

[dkoper]

Please copy NOTICE file when present with the LICENSE file.

Background:
With Apache licensed projects, it is super common (by ASF policy) to include a NOTICE file with the LICENSE for the copyright statements (unlike MIT, BSD etc. where the copyright statements are often at the top of the LICENSE).

The Apache 2.0 license also has a condition that redistribution requires copyright attributions in a NOTICE file (if present) are included in the distribution.

So at a recent audit, we were surprised to see none of our Apache licensed vendored dependencies had any NOTICE files with copyright statements. In our vendor folder they hadn't, but in the the original source repos they had! :)

Although NOTICE without file extension is most common (and preferred by the ASF), and covers our project's 11 Apache 2.0 licensed dependencies, it could have .md or .txt extensions as is common with LICENSE files.