chore: refine issue form and readme

Author: Justineo

.github/ISSUE_TEMPLATE/bug-report.en-US.yml

@@ -40,6 +40,6 @@ body:
     id: repro
     attributes:
       label: Reproduction
-      description: "A link to a boiled-down reproduction (a minimal but runnable demo with unnecessary dependencies pruned). Please paste the link to your CodeSandbox demo below: ([Vue 3 template](https://codesandbox.io/s/charming-night-2y6m6?file=/src/App.vue) / [Vue 2 template](https://codesandbox.io/s/suspicious-glitter-mk66j?file=/src/App.vue))"
+      description: "A link to a boiled-down reproduction (a minimal but runnable demo with unnecessary dependencies pruned). If the issue isn't reproducible within an online playground, please create a GitHub repo to reflect the problem. Please paste the link to your CodeSandbox demo or GitHub repo below: ([Vue 3 template](https://codesandbox.io/s/charming-night-2y6m6?file=/src/App.vue) / [Vue 2 template](https://codesandbox.io/s/suspicious-glitter-mk66j?file=/src/App.vue))"
     validations:
       required: true

.github/ISSUE_TEMPLATE/bug-report.zh-Hans.yml

@@ -40,6 +40,6 @@ body:
     id: repro
     attributes:
       label: 问题复现
-      description: "请提供一个精炼的问题复现（去除无关依赖的最小化可运行 demo）。 Plea请在下方贴入在 CodeSandbox 上 demo 的链接：（[Vue 3 模板](https://codesandbox.io/s/charming-night-2y6m6?file=/src/App.vue) / [Vue 2 模板](https://codesandbox.io/s/suspicious-glitter-mk66j?file=/src/App.vue)）"
+      description: "请提供一个精炼的问题复现（去除无关依赖的最小化可运行 demo）。如果在线环境无法复现，可以创建对应的 GitHub repo 来提供复现环境。请在下方贴入在 CodeSandbox 上 demo 的链接或 GitHub repo 链接：（[Vue 3 模板](https://codesandbox.io/s/charming-night-2y6m6?file=/src/App.vue) / [Vue 2 模板](https://codesandbox.io/s/suspicious-glitter-mk66j?file=/src/App.vue)）"
     validations:
       required: true

README.md

@@ -20,13 +20,21 @@ Not ready yet? Read documentation for older versions [here →](https://github.c
 $ npm install echarts vue-echarts
 ```
 
-To make `vue-echarts` work for Vue 2, you need to have `@vue/composition-api` installed:
+To make `vue-echarts` work for *Vue 2*, you need to have `@vue/composition-api` installed:
 
 ```sh
 npm i -D @vue/composition-api
 ```
 
-<details open>
+If you are using *NuxtJS* on top of *Vue 2*, you'll also need `@nuxtjs/composition-api`:
+
+```sh
+npm i -D @nuxtjs/composition-api
+```
+
+And then add `'@nuxtjs/composition-api/module'` in the `buildModules` option in your `nuxt.config.js`.
+
+<details>
 <summary>Vue 3</summary>
 
 ```js
@@ -108,7 +116,7 @@ import "echarts";
 
 #### SFC example
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 ```vue
@@ -299,7 +307,7 @@ export default {
 
 Drop `<script>` inside your HTML file and access the component via `window.VueECharts`.
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 <!-- vue3Scripts:start -->
@@ -402,7 +410,7 @@ See more examples [here](https://github.com/ecomfe/vue-echarts/tree/main/src/dem
 
 Vue-ECharts provides provide/inject API for `theme`, `init-options`, `update-options` and `loading-options` to help configuring contextual options. eg. for `init-options` you can use the provide API like this:
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 ```js

README.zh-Hans.md

@@ -18,13 +18,21 @@
 $ npm install echarts vue-echarts
 ```
 
-要在 Vue 2 下使用 `vue-echarts`，需要确保 `@vue/composition-api` 已经安装：
+要在 *Vue 2* 下使用 `vue-echarts`，需要确保 `@vue/composition-api` 已经安装：
 
 ```sh
 npm i -D @vue/composition-api
 ```
 
-<details open>
+如果你在使用基于 *Vue 2* 的 *NuxtJS*，那么还需要安装 `@nuxtjs/composition-api`：
+
+```sh
+npm i -D @nuxtjs/composition-api
+```
+
+然后在 `nuxt.config.js` 的 `buildModules` 选项中添加 `'@nuxtjs/composition-api/module'`。
+
+<details>
 <summary>Vue 3</summary>
 
 ```js
@@ -106,7 +114,7 @@ import "echarts";
 
 #### 单文件组件示例
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 ```vue
@@ -293,7 +301,7 @@ export default {
 
 用如下方式在 HTML 中插入 `<script>` 标签，并且通过 `window.VueECharts` 来访问组件接口：
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 <!-- vue3Scripts:start -->
@@ -392,7 +400,7 @@ Vue.component("v-chart", VueECharts);
 
 Vue-ECharts 为 `theme`、`init-options`、`update-options` 和 `loading-options` 提供了 provide/inject API，以通过上下文配置选项。例如：可以通过如下方式来使用 provide API 为 `init-options` 提供上下文配置：
 
-<details open>
+<details>
 <summary>Vue 3</summary>
 
 ```js