feat: automatically detect vue version

Author: antfu

README.md

@@ -86,7 +86,7 @@ export default {
 
 ## Vue 2 Support
 
-From `v0.7`, we support Vue 2 with [`vite-plugin-vue2`](https://github.com/underfin/vite-plugin-vue2)
+It just works.
 
 ```ts
 // vite.config.js
@@ -96,9 +96,7 @@ import ViteComponents from 'vite-plugin-components'
 export default {
   plugins: [
     createVuePlugin(),
-    ViteComponents({
-      transformer: 'vue2', // <--
-    }),
+    ViteComponents(),
   ],
 }
 ```

examples/vue2/vite.config.ts

@@ -5,9 +5,7 @@ import ViteComponents from 'vite-plugin-components'
 const config: UserConfig = {
   plugins: [
     createVuePlugin(),
-    ViteComponents({
-      transformer: 'vue2',
-    }),
+    ViteComponents(),
   ],
 }
 

src/index.ts

@@ -13,6 +13,9 @@ function VitePluginComponents(options: Options = {}): Plugin {
     name: 'vite-plugin-components',
     enforce: 'post',
     configResolved(config) {
+      if (config.plugins.find(i => i.name === 'vite-plugin-vue2'))
+        options.transformer = options.transformer || 'vue2'
+
       ctx = new Context(options, config)
       transformers = [
         ctx.options.transformer === 'vue2'