feat: upgrade to eslint v7!

[satazor]

The following packages will emit a warning saying they need eslint v6, but the warning can be ignored:

• eslint-config-react-native due to eslint-plugin-react-native
• eslint-config-react-native-a11y due to eslint-plugin-react-native-a11y

BREAKING CHANGE: all packages have now a peerDependency on eslint v7

[codecov[bot]]

Codecov Report

Merging #108 into master will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #108   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           49        49           
  Lines           61        61           
  Branches         1         1           
=========================================
  Hits            61        61           

Impacted Files	Coverage Δ
packages/eslint-config-babel/lib/index.js	100.00% <100.00%> (ø)

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