docs: website for LiquidJS

docs/source/tutorials/use-in-expressjs.md

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+---
+title: Use in Express.js
+---
+
+LiquidJS is compatible to the [express template engines](https://expressjs.com/en/resources/template-engines.html). You can set liquidjs instance to the [view engine][express-views] option:
+
+```javascript
+var { Liquid } = require('liquidjs');
+var engine = new Liquid();
+
+// register liquid engine
+app.engine('liquid', engine.express()); 
+app.set('views', './views');            // specify the views directory
+app.set('view engine', 'liquid');       // set liquid to default
+```
+
+{% note info Working Demo %} Here's a working demo for LiquidJS usage in Express.js: <a href="https://github.com/harttle/liquidjs/blob/master/demo/express/" target="_blank">liquidjs/demo/express/</a>.{% endnote %}
+
+## Template Lookup
+
+The [root][root] option will continue to work as templates root, as you can see in [Render A Template File][render-a-file]. Additionally, the [`views`][express-views] option in express.js (as shown above) will also be respected. Say you have a template directory like:
+
+```
+.
+├── views1/
+│ └── hello.liquid
+└── views2/
+  └── world.liquid
+```
+
+And you're setting template root for liquidjs to `views1` and expressjs to `views2`:
+
+```javascript
+var { Liquid } = require('liquidjs');
+var engine = new Liquid({
+    root: './views1/'
+});
+
+app.engine('liquid', engine.express()); 
+app.set('views', './views2');            // specify the views directory
+app.set('view engine', 'liquid');       // set liquid to default
+```
+
+Both of `hello.liquid` and `world.liquid` can be resolved and rendered:
+
+```javascript
+res.render('hello')
+res.render('world')
+```
+
+## Caching
+
+Simply setting the [cache option][cache] to true will enable template caching, as explained in [Caching][Caching]. It's recommended to enable cache in production environment, which can be done by:
+
+```javascript
+var { Liquid } = require('liquidjs');
+var engine = new Liquid({
+    cache: process.env.NODE_ENV === 'production'
+});
+```
+
+[cache]: ../api/interfaces/liquid_options_.liquidoptions.html#Optional-cache
+[express-views]: http://expressjs.com/en/guide/using-template-engines.html
+[parseFile]: ../api/classes/liquid_.liquid.html#parseFile
+[parseFileSync]: ../api/classes/liquid_.liquid.html#parseFileSync
+[layout]: https://help.shopify.com/en/themes/liquid/tags/theme-tags#layout
+[include]: https://help.shopify.com/themes/liquid/tags/theme-tags#include
+[root]: ../api/interfaces/liquid_options_.liquidoptions.html#Optional-root
+[render-a-file]: ./render-a-file.html
+[Caching]: ./caching.html