Fix(docs): fix and update docs. (dxfjs#33)

Co-authored-by: EL JABIRI Tarik <[email protected]>

Author: DeepankarGupta13

docs/.vitepress/config.ts

@@ -45,7 +45,7 @@ export default defineConfig({
 				collapsible: true,
 				items: [
 					{ text: 'Introduction', link: '/guide/' },
-					{ text: 'Variables', link: '/guide/variables' },
+					{ text: 'Header', link: '/guide/header' },
 					{ text: 'Tables', link: '/guide/tables' },
 					{ text: 'Blocks', link: '/guide/blocks' },
 					{ text: 'Entities', link: '/guide/entities' },

docs/guide/header.md

@@ -0,0 +1,73 @@
+---
+layout: doc
+---
+
+# Header
+
+## Variables
+
+Variables contains settings associated with the drawing, defined in the `HEADER` section.
+> All possible [variables](https://help.autodesk.com/view/OARX/2023/ENU/?guid=GUID-A85E8E67-27CD-4C59-BE61-4DC9FADBE74A)
+
+:::info
+
+By default these variables are set automatically:
+
+- `$ACADVER` The AutoCAD drawing database version number: AC1021 = AutoCAD 2007.
+- `$HANDSEED` Next available handle.
+- `$INSUNITS` Default drawing units for AutoCAD DesignCenter blocks: 0 = Unitless.
+- `$VIEWCTR` XY center of current view on screen.
+- `$CLAYER` Save the current layer name.
+- `$LASTSAVEDBY` Sets to the package name.
+
+:::
+
+## Adding variables
+
+Each variable is specified by a 9 group code giving the variable's name, followed by groups that supply the variable's value:
+
+```txt
+  9
+$NAME // The name of the variable.
+  10  // First group code
+20    // The value assocoated
+  20  // Second group code
+20    // The value assocoated
+// And so on...
+
+// These values are random.
+```
+
+Javascript code :
+
+```js
+import { DxfWriter } from "@tarikjabiri/dxf";
+const dxf = new DxfWriter();
+dxf.setVariable("$ATTMODE", { 70: 2 });
+// $ATTMODE is the name of the variable
+// 70 is the group code
+// 2 is the value to be set.
+dxf.setVariable("$PLIMMAX", {
+  10: 20,
+  20: 30,
+}); // This variable accept tow group codes and tow values
+```
+
+:::info
+
+- The object passed as values is key value paired, the key is the group code and value associated with it.
+- If you try to add a variable already added, its values will be updated.
+
+:::
+
+## Setting Units
+
+To set units use the convenient method `setUnits()`:
+
+```js
+import { DxfWriter, Units } from '@tarikjabiri/dxf';
+
+const dxf = new DxfWriter();
+dxf.setUnits(Units.Meters);
+
+```