remove injectCSS

packages/core/src/utils/injectCSS.ts

@@ -1,13 +0,0 @@
-export default function injectCSS(css: string) {
-  const style = document.createElement('style')
-  style.type = 'text/css'
-  style.textContent = css
-  const { head } = document
-  const { firstChild } = head
-
-  if (firstChild) {
-    return head.insertBefore(style, firstChild)
-  } else {
-    return head.appendChild(style)
-  }
-}