fix: use relative path for self path resolution

Author: yyx990803

Diff for: lib/loaders/pitch.js

@@ -1,6 +1,6 @@
 const qs = require('querystring')
 const loaderUtils = require('loader-utils')
-const selfPath = require.resolve('vue-loader')
+const selfPath = require.resolve('../index')
 const templateLoaderPath = require.resolve('./templateLoader')
 const stylePostLoaderPath = require.resolve('./stylePostLoader')