Replace setCode with deferredSetCode in App (#649)

* Replace `setCode` with `deferredSetCode` in App

* Remove unused OpenFileButton component

src/components/OpenFileButton.tsx

@@ -1,42 +0,0 @@
-import { invoke } from '@tauri-apps/api/tauri'
-import { open } from '@tauri-apps/api/dialog'
-import { useStore } from '../useStore'
-
-export const OpenFileButton = () => {
-  const { setCode } = useStore((s) => ({
-    setCode: s.setCode,
-  }))
-  const handleClick = async () => {
-    const selected = await open({
-      multiple: false,
-      directory: false,
-      filters: [
-        {
-          name: 'CAD',
-          extensions: ['toml'],
-        },
-      ],
-    })
-    if (Array.isArray(selected)) {
-      // User selected multiple files
-      // We should not get here, since multiple is false.
-    } else if (selected === null) {
-      // User cancelled the selection
-      // Do nothing.
-    } else {
-      // User selected a single file
-      // We want to invoke our command to read the file.
-      const json: string = await invoke('read_toml', { path: selected })
-      const packageDetails = JSON.parse(json).package
-      if (packageDetails.main) {
-        const absPath = [
-          ...selected.split('/').slice(0, -1),
-          packageDetails.main,
-        ].join('/')
-        const file: string = await invoke('read_txt_file', { path: absPath })
-        setCode(file)
-      }
-    }
-  }
-  return <button onClick={() => handleClick()}>Open File</button>
-}