refactor(graphcontext): memoize context

src/ConnectionLine/index.js

@@ -1,4 +1,4 @@
-import React, { useEffect, useState } from 'react';
+import React, { useEffect, useState, memo } from 'react';
 import cx from 'classnames';
 
 export default (props) => {
@@ -41,4 +41,4 @@ export default (props) => {
       />
     </g>
   );
-};
+};