doc: update

Author: kaiwk

README.md

@@ -3,6 +3,32 @@
 
 LeetCode brings you offer, and now Emacs brings you LeetCode!
 
+# Usage
+
+![screencast](images/screencast.gif)
+
+1. Execute `leetcode` command, and in problem list buffer:
+
+| keymap | command                                |
+|--------|----------------------------------------|
+| n      | cursor move down                       |
+| p      | cursor move up                         |
+| s      | filter problems by regex               |
+| t      | filter problems by tag                 |
+| d      | filter problems by difficulty          |
+| /      | clear filters                          |
+| g      | refresh without fetching from LeetCode |
+| G      | refresh all data                       |
+| RET    | show current problem description       |
+
+2. Press `<RET>`, show problem description, move cursor to "solve it", press
+   `<RET>` again, start coding!
+
+3. After finishing your code, you can edit testcase and execute `leetcode-try`
+   or execute `leetcode-submit`.
+
+![leetcode-submit](images/leetcode-submit.png)
+
 # Installation
 
 - Vanilla Emacs: `package-install` it from melpa directly
@@ -41,34 +67,6 @@ You can save solution by setting `leetcode-save-solutions`:
 (setq leetcode-directory "~/leetcode")
 ```
 
-# Usage
-
-1. Execute `leetcode` command.
-
-![leetcode](images/leetcode.png)
-
-In leetcode problems list buffer:
-
-| keymap | command                                |
-|--------|----------------------------------------|
-| n      | cursor move down                       |
-| p      | cursor move up                         |
-| s      | filter problems by regex               |
-| t      | filter problems by tag                 |
-| d      | filter problems by difficulty          |
-| /      | clear filters                          |
-| g      | refresh without fetching from LeetCode |
-| G      | refresh all data                       |
-| RET    | show current problem description       |
-
-2. Press `<RET>`, show problem description, move cursor to "solve it", press
-   `<RET>` again, start coding!
-
-3. After finishing your code, you can edit testcase and execute `leetcode-try`
-   or execute `leetcode-submit`.
-
-![leetcode-submit](images/leetcode-submit.png)
-
 # Debug
 
 Call `leetcode-toggle-debug`, log will output in `*leetcode-log*` buffer.