docs(aliases): clarify usage (#9990)

plugins/aliases/README.md

-## Aliases Cheatsheet
+# Aliases cheatsheet
 
 **Maintainer:** [@hqingyi](https://github.com/hqingyi)
 
 With lots of 3rd-party amazing aliases installed, this plugin helps list the shortcuts
 that are currently available based on the plugins you have enabled.
 
-Enable this plugin by adding it to your `plugins` definition in `~/.zshrc`.
+To use it, add `aliases` to the plugins array in your zshrc file:
 
-  ```
-  plugins=(aliases)
-  ```
+```zsh
+plugins=(aliases)
+```
 
 Requirements: Python needs to be installed.
 
-### Usage
+## Usage
 
-```
-  acs: group all alias
-  acs $keywordquickly filter alias & highlight
-```
+- `acs`: show all aliases by group.
+
+- `acs <keyword>`: filter aliases by `<keyword>` and highlight.
+
+  ![screenshot](https://cloud.githubusercontent.com/assets/3602957/11581913/cb54fb8a-9a82-11e5-846b-5a67f67ad9ad.png)