utf-8 declrations just in case

background.html

@@ -1 +1 @@
-<html><body><script src="background-script.js" charset="UTF-8"></script><textarea id="nazeka-paste-target"></textarea></body></html>
+<html><head><meta charset="utf-8"/></head><body><script src="background-script.js" charset="UTF-8"></script><textarea id="nazeka-paste-target"></textarea></body></html>