Add default shadow outline utility

Author: reinink

__tests__/fixtures/tailwind-output.css

@@ -3575,6 +3575,10 @@ button,
   box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, .06);
 }
 
+.shadow-outline {
+  box-shadow: 2px solid rgba(52, 144, 220, .5);
+}
+
 .shadow-none {
   box-shadow: none;
 }
@@ -7480,6 +7484,10 @@ button,
     box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, .06);
   }
 
+  .sm\:shadow-outline {
+    box-shadow: 2px solid rgba(52, 144, 220, .5);
+  }
+
   .sm\:shadow-none {
     box-shadow: none;
   }
@@ -11378,6 +11386,10 @@ button,
     box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, .06);
   }
 
+  .md\:shadow-outline {
+    box-shadow: 2px solid rgba(52, 144, 220, .5);
+  }
+
   .md\:shadow-none {
     box-shadow: none;
   }
@@ -15276,6 +15288,10 @@ button,
     box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, .06);
   }
 
+  .lg\:shadow-outline {
+    box-shadow: 2px solid rgba(52, 144, 220, .5);
+  }
+
   .lg\:shadow-none {
     box-shadow: none;
   }
@@ -19174,6 +19190,10 @@ button,
     box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, .06);
   }
 
+  .xl\:shadow-outline {
+    box-shadow: 2px solid rgba(52, 144, 220, .5);
+  }
+
   .xl\:shadow-none {
     box-shadow: none;
   }

defaultConfig.stub.js

@@ -728,6 +728,7 @@ module.exports = {
     'md': '0 4px 8px 0 rgba(0,0,0,0.12), 0 2px 4px 0 rgba(0,0,0,0.08)',
     'lg': '0 15px 30px 0 rgba(0,0,0,0.11), 0 5px 15px 0 rgba(0,0,0,0.08)',
     'inner': 'inset 0 2px 4px 0 rgba(0,0,0,0.06)',
+    'outline': '2px solid rgba(52,144,220,0.5)',
     'none': 'none',
   },