Create documentation for landline validator

Author: vahidkaargar

docs/1.x/valid-landline-number.md

@@ -0,0 +1,33 @@
+## ValidLandlineNumber
+
+If you want to validate the landline number, you can use the `ValidLandlineNumber` rule:
+
+```php
+use Milwad\LaravelValidate\Rules\ValidLandlineNumber;
+
+return [
+    'landline-number' => ['required', new ValidLandlineNumber()], // landline-number => 09120000000
+];
+```
+
+Also `ValidLandlineNumber` have the ability to validate landline number with specific country code:
+
+```php
+use Milwad\LaravelValidate\Rules\ValidLandlineNumber;
+use Milwad\LaravelValidate\Utils\Country;
+
+return [
+    'landline-number' => ['required', new ValidLandlineNumber(Country::GERMANY)], // landline-number => 09120000000
+];
+```
+
+> **Note**  
+> If you want to know which country's codes are supported by the `ValidLandlineNumber` Rule, you can search your country
+> on this [Countries Landline Number](#support-countries-landline-number) list.
+
+<a name="support-countries-landline-number"></a>
+## Support Countries Landline Number
+
+- ✅ IRAN
+- ✅ GERMANY
+