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` <a href="https://www.npmjs.com/package/postcss-custom-properties">(=> postcss-custom-properties)</a>
+- `calc` <a href="https://www.npmjs.com/package/postcss-calc">(=> postcss-calc)</a>
+- `customMedia` <a href="https://www.npmjs.com/package/postcss-custom-media">(=> postcss-custom-media)</a>
+- `mediaQueriesRange` <a href="https://www.npmjs.com/package/postcss-media-minmax">(=> postcss-media-minmax)</a>
+- `customSelectors` <a href="https://www.npmjs.com/package/postcss-custom-selectors">(=> postcss-custom-selectors)</a>
+- `colorRebeccapurple` <a href="https://www.npmjs.com/package/postcss-color-rebeccapurple">(=> postcss-color-rebeccapurple)</a>
+- `colorHwb` <a href="https://www.npmjs.com/package/postcss-color-hwb">(=> postcss-color-hwb)</a>
+- `colorGray` <a href="https://www.npmjs.com/package/postcss-color-gray">(=> postcss-color-gray)</a>
+- `colorHexAlpha` <a href="https://www.npmjs.com/package/postcss-color-hex-alpha">(=> postcss-color-hex-alpha)</a>
+- `colorFunction` <a href="https://www.npmjs.com/package/postcss-color-function">(=> postcss-color-function)</a>
+- `fontVariant` <a href="https://www.npmjs.com/package/postcss-font-variant">(=> postcss-font-variant)</a>
+- `filter` <a href="https://www.npmjs.com/package/pleeease-filters">(=> pleeease-filters)</a>
+- `rem` <a href="https://www.npmjs.com/package/pixrem">(=> pixrem)</a>
+- `pseudoElements` <a href="https://www.npmjs.com/package/postcss-pseudoelements">(=> postcss-pseudoelements)</a>
+- `pseudoClassMatches` <a href="https://www.npmjs.com/package/postcss-selector-matches">(=> postcss-selector-matches)</a>
+- `pseudoClassNot` <a href="https://www.npmjs.com/package/postcss-selector-not">(=> postcss-selector-not)</a>
+- `colorRgba` <a href="https://www.npmjs.com/package/postcss-color-rgba-fallback">(=> postcss-color-rgba-fallback)</a>
+- `autoprefixer` <a href="https://www.npmjs.com/package/autoprefixer-core">(=> autoprefixer-core)</a>
 
 _Note: order is important to get everything working correctly._