Disallow declaration of global variables

[foray1010]

'no-shadow': [2, {'builtinGlobals': true, 'hoist': 'functions', 'allow': []}],

[ljharb]

would you mind adding a new comment line linking to the rule definition (http://eslint.org/docs/rules/no-shadow.html)?

[ljharb]

This might also be nice to reference somewhere in the actual guide. LGTM overall, pending 2 comments.

[foray1010]

Updated according to the comments

[foray1010]

enabling this will disable the use of a lot of variables when env browser is true, such as name and length
See https://github.com/sindresorhus/globals/blob/master/globals.json#L164

My team disable browser because most of our projects are backend
but for airbnb, I think you guys may have different preference
Feel free to close this PR

[ljharb]

I don't want the JS builtins shadowed, but that's a good point - given that it includes all environment builtins, perhaps this would be a bit too restrictive.