refacor: customCSS 코드 분리

hwe/ts/util/customCSS.ts

@@ -0,0 +1,9 @@
+export function insertCustomCSS(key = 'sam_customCSS'){
+    const customCSS = localStorage.getItem(key);
+    if (customCSS) {
+        const css = document.createElement('style');
+        css.innerHTML = customCSS;
+        console.log(css);
+        document.getElementsByTagName('head')[0].appendChild(css);
+    }
+}