Use full Apache License 2.0 text in LICENSE

[BigBlueHat]

Description

This PR adds the full license text of the Apache License 2.0 per the license application guidelines from the Apache Software Foundation:
https://www.apache.org/foundation/license-faq.html#Apply-My-Software

The current contents of the LICENSE file is meant for source file headers, not the LICENSE file.

Motivation and Context

This properly applies the Apache License 2.0 to this repository. Though, a more thorough application of the license would be to apply the license notice to each source file in this repository--see "How should I apply the Apache License to my own software?" for more information.

How Has This Been Tested?

Years of OSS compliance work and study. 😄

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[hkosova]

This PR looks like a duplicate of #5470.

[webron]

Closing in favor of #5470.