types: should import type 'Plugin' from 'vue-demi' instead of 'vue'

Author: cloydlau

src/install.ts

@@ -1,17 +1,17 @@
-import type { Plugin } from 'vue'
 import { useGlobalConfig } from 'vue-global-config'
+import type { Plugin, install } from 'vue-demi'
 import Component from './Component'
 import type { Mode } from './Component'
 
-type SFCWithInstall<T> = T & Plugin
+type SFCWithInstall<T> = T & Plugin & { install: typeof install }
 
 const withInstall = <T, E extends Record<string, any>>(
   main: T,
   extra?: E,
 ) => {
   (main as SFCWithInstall<T>).install = (app): void => {
     for (const comp of [main, ...Object.values(extra ?? {})]) {
-      app.component(comp.name, comp)
+      app?.component(comp.name, comp)
     }
   }