Added link to all postcss plugin

Author: magsout

docs/content/usage.md

@@ -56,24 +56,24 @@ var output = cssnext(input, {
 
 To know all available options, please check corresponding postcss plugin:
 
-- `customProperties` (=> postcss-custom-properties)
-- `calc` (=> postcss-calc)
-- `customMedia` (=> postcss-custom-media)
-- `mediaQueriesRange` (=> postcss-media-minmax)
-- `customSelectors` (=> postcss-custom-selectors)
-- `colorRebeccapurple` (=> postcss-color-rebeccapurple)
-- `colorHwb` (=> postcss-color-hwb)
-- `colorGray` (=> postcss-color-gray)
-- `colorHexAlpha` (=> postcss-color-hex-alpha)
-- `colorFunction` (=> postcss-color-function)
-- `fontVariant` (=> postcss-font-variant)
-- `filter` (=> pleeease-filters)
-- `rem` (=> pixrem)
-- `pseudoElements` (=> postcss-pseudoelements)
-- `pseudoClassMatches` (=> postcss-selector-matches)
-- `pseudoClassNot` (=> postcss-selector-not)
-- `colorRgba` (=> postcss-color-rgba-fallback)
-- `autoprefixer` (=> autoprefixer-core)
+- `customProperties` [(=> postcss-custom-properties)](https://www.npmjs.com/package/postcss-custom-properties)
+- `calc` [(=> postcss-calc)](https://www.npmjs.com/package/postcss-calc)
+- `customMedia` [(=> postcss-custom-media)](https://www.npmjs.com/package/postcss-custom-media)
+- `mediaQueriesRange` [(=> postcss-media-minmax)](https://www.npmjs.com/package/postcss-media-minmax)
+- `customSelectors` [(=> postcss-custom-selectors)](https://www.npmjs.com/package/postcss-custom-selectors)
+- `colorRebeccapurple` [(=> postcss-color-rebeccapurple)](https://www.npmjs.com/package/postcss-color-rebeccapurple)
+- `colorHwb` [(=> postcss-color-hwb)](https://www.npmjs.com/package/postcss-color-hwb)
+- `colorGray` [(=> postcss-color-gray)](https://www.npmjs.com/package/postcss-color-gray)
+- `colorHexAlpha` [(=> postcss-color-hex-alpha)](https://www.npmjs.com/package/postcss-color-hex-alpha)
+- `colorFunction` [(=> postcss-color-function)](https://www.npmjs.com/package/postcss-color-function)
+- `fontVariant` [(=> postcss-font-variant)](https://www.npmjs.com/package/postcss-font-variant)
+- `filter` [(=> pleeease-filters)](https://www.npmjs.com/package/pleeease-filters)
+- `rem` [(=> pixrem)](https://www.npmjs.com/package/pixrem)
+- `pseudoElements` [(=> postcss-pseudoelements)](https://www.npmjs.com/package/postcss-pseudoelements)
+- `pseudoClassMatches` [(=> postcss-selector-matches)](https://www.npmjs.com/package/postcss-selector-matches)
+- `pseudoClassNot` [(=> postcss-selector-not)](https://www.npmjs.com/package/postcss-selector-not)
+- `colorRgba` [(=> postcss-color-rgba-fallback)](https://www.npmjs.com/package/postcss-color-rgba-fallback)
+- `autoprefixer` [(=> autoprefixer-core)](https://www.npmjs.com/package/autoprefixer-core)
 
 _Note: order is important to get everything working correctly._