Introduced @shopgate/engage package to start new API

[devbucket]

Type of change

Please add an "x" into the option that is relevant:

• [ ] Bug Fix 🐛 (non-breaking change which fixes an issue)
• [ x ] New Feature 🚀 (non-breaking change which adds functionality)
• [ ] Breaking Change 💥 (fix or feature that would cause existing functionality to not work as expected)
• [ ] Polish 💅 (Just some cleanups)
• [ ] Docs 📝 (Changes in the documentations)
• [ ] Internal 🏠 Only relates to internal processes.

How to test it

Please describe here any specialty that the tester should be aware of.

[coveralls]

Pull Request Test Coverage Report for Build 2320

• 0 of 4 (0.0%) changed or added relevant lines in 2 files are covered.
• 10 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.1%) to 50.969%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/commerce/checkout/index.js	0	1	0.0%
libraries/commerce/scanner/index.js	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
libraries/commerce/product/action-creators/setProductVariantId.js	2	0.0%
libraries/commerce/product/action-creators/setProductId.js	2	0.0%
libraries/commerce/product/actions/processProductFlags.js	6	0.0%

Totals
Change from base Build 2305:	0.1%
Covered Lines:	5729
Relevant Lines:	10625

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💛 - Coveralls