chore: lazy-require compiler in case user provides custom compiler

lib/loaders/templateLoader.js

 const qs = require('querystring')
 const loaderUtils = require('loader-utils')
-const compiler = require('vue-template-compiler')
 const { compileTemplate } = require('@vue/component-compiler-utils')
 const { genTemplateHotReloadCode } = require('../codegen/hotReload')
 
@@ -22,6 +21,8 @@ module.exports = function (source) {
   const isFunctional = query.functional
   const needsHotReload = !isServer && !isProduction && options.hotReload !== false
 
+  // allow using custom compiler via options
+  const compiler = options.compiler || require('vue-template-compiler')
   const compilerOptions = Object.assign({}, options.compilerOptions, {
     scopeId: query.scoped ? `data-v-${id}` : null,
     comments: query.comments
@@ -31,8 +32,7 @@ module.exports = function (source) {
   const finalOptions = {
     source,
     filename: this.resourcePath,
-    // allow using custom compiler via options
-    compiler: options.compiler || compiler,
+    compiler,
     compilerOptions,
     // handle possible lang="xxx"
     preprocessLang: query.lang,