rewrite responsive docs

Author: moondda

responsive.md

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+# Responsive
+
+Devup UI supports responsive design.
+
+# Breakpoints
+
+Devup UI provides flexible responsive design capabilities through breakpoints. You can use either the default breakpoint system or customize your own breakpoints to match your design requirements.
+
+## Default Breakpoints
+
+By default, Devup UI uses a 5-breakpoint system with the following viewport ranges:
+
+| Index | Viewport Range | Description     |
+| ----- | -------------- | --------------- |
+| 1st   | ~ 479px        | Mobile (small)  |
+| 2nd   | 480px ~ 767px  | Mobile (large)  |
+| 3rd   | 768px ~ 991px  | Tablet          |
+| 4th   | 992px ~ 1279px | Desktop (small) |
+| 5th   | 1280px ~       | Desktop (large) |
+
+## Using Responsive Arrays
+
+You can add responsive design by using an array of maximum 5 elements for any style property:
+
+```jsx
+const box = (
+  <Box bg={["red", "blue", "green", "yellow", "purple"]} w={25} h={25}>
+    <Text>Hello</Text>
+  </Box>
+);
+```
+
+### Null Values
+
+If any of the five elements are set to `null`, Devup UI uses the previous value for responsive design:
+
+```jsx
+// Background will be:
+// - red from 0px to 767px (1st and 2nd breakpoints)
+// - green from 768px to 1279px (3rd and 4th breakpoints)
+// - purple from 1280px and above (5th breakpoint)
+<Box bg={["red", null, "green", null, "purple"]} />
+```
+
+### Partial Arrays
+
+If the length of the array is less than 5, Devup UI makes responsive design according to the index of the element:
+
+```jsx
+// Only specify mobile and desktop values
+<Box bg={['red', 'blue']} /> // red for mobile, blue for larger screens
+
+// Specify mobile, tablet, and desktop
+<Box bg={['red', 'blue', 'green']} />
+```
+
+## Custom Breakpoints
+
+You can customize breakpoints by adding a `breakpoints` configuration to your `devup.json` file:
+
+### Configuration
+
+```json
+{
+  "theme": {
+    "breakpoints": [0, 460, 768, 1024]
+  }
+}
+```
+
+### How Custom Breakpoints Work
+
+When you define custom breakpoints, the array values correspond to minimum viewport widths:
+
+- **1st element**: From 0px to the first breakpoint value
+- **2nd element**: From first breakpoint to second breakpoint
+- **3rd element**: From second breakpoint to third breakpoint
+- **And so on...**
+
+### Example with Custom Breakpoints
+
+```json
+// create devup.json
+{
+  "theme": {
+    "breakpoints": [0, 460, 1024]
+  }
+}
+```
+
+```jsx
+// With the custom breakpoints above:
+<Box bg={["red", "blue", "green"]} />
+```
+
+This would create the following responsive behavior:
+
+- `red` background from 0px to 459px
+- `blue` background from 460px to 1023px
+- `green` background from 1024px and above