perf: improve performance by 4x by simplified parseFile

- previously deprecated `getTemplate()` and `getTemplateSync()` not no longer supported
- `opts` no longer support dynamic set in `parseFile()`, `renderFile()` arguments

docs/source/tutorials/contribution-guidelines.md

@@ -4,7 +4,7 @@ title: Contribution Guideline
 
 ## Star on Github 👉 [![harttle/liquidjs](https://img.shields.io/github/stars/harttle/liquidjs?style=flat-square)][liquidjs]
 
-Staring us is the most important and easiest way to support us: boost its rank and expose it to more people, which in turn makes it better.
+Staring LiquidJS is the most important and easiest way to support us: boost its rank and expose it to more people, which in turn makes it better.
 
 ## Show Me Your Code
 
@@ -22,6 +22,8 @@ npm test
 
 **Commit Message**: Please align to [the Angular Commit Message Guidelines](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#commits), especially note the [type identifier](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#type), on which semantic-release bot depends.
 
+**Backward-Compatibility**: please be backward-compatible. LiquidJS is used by multiple layers of softwares, including underlying libraries, compilers, site generators and Web servers. It's not easy to do a major upgrade for most of them.
+
 ## Financial Support
 
 LiquidJS is Open Source and Free and **without** capitalists support and **without** any ADs. To help it live and thrive, consider contribute on [Open Collective][oc] or [Patreon][pt]. To acknowledge your contribution, your name and avatar will be listed here and on [Github README][liquidjs].

docs/source/zh-cn/tutorials/contribution-guidelines.md

@@ -22,6 +22,8 @@ npm test
 
 **提交消息**：请遵守 [Angular 提交消息规范](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#commits)，尤其注意 [type 标识](https://github.com/angular/angular.js/blob/master/DEVELOPERS.md#type)，semantic-release 机器人依赖这个标识自动发布。
 
+**向后兼容**：请考虑向后（之前的旧的版本）兼容。LiquidJS 被用于很多层的软件，包括底层库、编译器、站点生成器、 Web 服务器。对多数最终用户来说，驱动或请求整个系统做一次主版本升级是很难办到的。
+
 ## 成为赞助者！
 
 LiquidJS 是开源的、免费的，并且 **没有** 商业支持，也 **没有** 任何广告。如果你喜欢 LiquidJS 或你的公司在使用 LiquidJS，请考虑通过 [Open Collective][oc] 或 [Patreon][pt] 赞助，作为感谢你的名字和头像（或 Logo）会展示在这里和 [Github README][liquidjs]。