Add sync modifier to v-bind (#28)

Author: Guillaume Chau

Diff for: lib/rules/no-invalid-v-bind.js

@@ -15,7 +15,7 @@ const utils = require('../utils')
 // Helpers
 // ------------------------------------------------------------------------------
 
-const VALID_MODIFIERS = new Set(['prop', 'camel'])
+const VALID_MODIFIERS = new Set(['prop', 'camel', 'sync'])
 
 /**
  * Creates AST event handlers for no-invalid-v-bind.