add keybinding-emacs of ace-builds (#2337)

Co-authored-by: qlq <[email protected]>

Author: qlq3763

src/content_scripts/ace.js

@@ -1,5 +1,6 @@
 import "ace-builds/src-noconflict/ace";
 import "ace-builds/src-noconflict/ext-language_tools";
 import "ace-builds/src-noconflict/keybinding-vim";
+import "ace-builds/src-noconflict/keybinding-emacs";
 import "ace-builds/src-noconflict/mode-javascript";
 import "ace-builds/src-noconflict/theme-chrome";