Fix ambiguous default export

Removes default export of plugin and replaces it with const export.

BREAKING CHANGE: plugin is now exported using `plugin` export, rather
than the default export.

docs/.vitepress/theme/index.js

@@ -1,5 +1,5 @@
 import DefaultTheme from 'vitepress/theme'
-import Omorphia from 'omorphia'
+import { plugin as Omorphia } from 'omorphia'
 import DemoContainer from './DemoContainer.vue'
 
 import './compat.scss'

lib/index.ts

@@ -2,14 +2,13 @@ import * as components from './components/index.js'
 import FloatingVue from 'floating-vue'
 import { Plugin } from 'vue'
 
-const plugin: Plugin = (app) => {
+export const plugin: Plugin = (app) => {
   for (const key in components) {
     app.component(key, components[key as keyof typeof components])
   }
   app.use(FloatingVue)
 }
 
-export default plugin
 export * from './components/index.js'
 export * from './helpers/index.js'