feat(assets): bundle runtime assets and vendor dependencies

vendor/yomitan/background.html

@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="UTF-8">
+    <title>Yomitan Background</title>
+</head>
+<body>
+    <script type="module" src="js/background/background-main.js"></script>
+</body>
+</html>