Add background-origin utilities (#4117)

* Add background-origin utilities

* Update fixtures

* Update basic usage test

* Change sort order for background origin

* Move background origin after other background properties

src/corePluginList.js

@@ -17,6 +17,7 @@ export const corePluginList = [
   'backgroundPosition',
   'backgroundRepeat',
   'backgroundSize',
+  'backgroundOrigin',
   'borderCollapse',
   'borderColor',
   'borderOpacity',

src/plugins/backgroundOrigin.js

@@ -0,0 +1,12 @@
+export default function () {
+  return function ({ addUtilities, variants }) {
+    addUtilities(
+      {
+        '.bg-origin-border': { 'background-origin': 'border-box' },
+        '.bg-origin-padding': { 'background-origin': 'padding-box' },
+        '.bg-origin-content': { 'background-origin': 'content-box' },
+      },
+      variants('backgroundOrigin')
+    )
+  }
+}

src/plugins/index.js

@@ -23,6 +23,7 @@ export { default as backgroundOpacity } from './backgroundOpacity'
 export { default as backgroundPosition } from './backgroundPosition'
 export { default as backgroundRepeat } from './backgroundRepeat'
 export { default as backgroundSize } from './backgroundSize'
+export { default as backgroundOrigin } from './backgroundOrigin'
 export { default as blur } from './blur'
 export { default as borderCollapse } from './borderCollapse'
 export { default as borderColor } from './borderColor'