Add whitelist/blacklist for CSS properties

[henryruhs]

Thank you very much for this great plugin.

In some cases this plugin is buggy, for the moment we can fix most of it using the ignore comments.

Another, more cleaner way from my point of view would be a whitelist/blacklist for CSS properties to be passed via the options. In other words: this plugin generates tons of RTL / LTR rules that we don't need so give us the power what RTL declarations should be generated.

Only process declarations that include margin-right and border-right:

require('postcss-rtl')({
     whitelist: [
         'margin-right',
         'border-right'
     ]
});

Use the default preset but ignore padding at all:

require('postcss-rtl')({
     blacklist: [
         'padding'
     ]
});

Do you need a helpful hand? Let me know!

[vkalinichev]

Released in 1.7.0:

• blacklist: the array of css properties which processing will be ignored
  Example:

  ['padding-left', 'padding-right']

• whitelist: the array of css properties which (and only them) will be processed
  Example:

  ['margin', 'border-color']

Thank you for proposal!

[miladmeidanshahi]

@vkalinichev what about CSS files?