serial-number

Markdown automatic add serial number.

Example

1. Automatically read clipborad content.

2. Write to clipboard after add serial number.

# title

## heading2-1

### heading3-1

### heading3-2

## heading2-2

## heading2-3

# title

## 1. heading2-1

### 1.1. heading3-1

### 1.2. heading3-2

## 2. heading2-2

## 3. heading2-3