Build: Add browser policy and eslint plugin

[yomed]

Description

• condense browser policy into a browserslist definition
• use this list to drive eslint-plugin-compat

Context

This helps define our browser support both internally and externally. The eBay policy has 3 tiers, so effectively we need to support tier 1 and 2 (as a component library). We could delineate the exact tiers and browsers, but I don't really want to repeat either the actual eBay Browser Policy or our browserslist.

References

https://github.com/amilajack/eslint-plugin-compat
#53
#54

Screenshots

Failure looks like this:

  174:5  error  fetch is not supported in Safari 6, iOS Safari 7.0-7.1, IE Mobile 10, IE 9, Edge 12, Android Browser 3  compat/compat

✖ 1 problem (1 error, 0 warnings)

error An unexpected error occurred: "Command failed.

[coveralls]

Pull Request Test Coverage Report for Build 236

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.96%

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Totals
Change from base Build 216:	0.0%
Covered Lines:	406
Relevant Lines:	448

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💛 - Coveralls

[seangates]

Eventually this should come from a global require, correct? We store it in the @eBay org? https://github.com/browserslist/browserslist#shareable-configs

/cc @senthilp

[senthilp]

Yes, that is the plan. For now, this should be ok.

[seangates]

I've created a task to track and prioritize it: #76.

[ianmcburnie]

Super dooper!