docs: added PasswordStrength rule

Author: andrepimpao

docs/03-rules.md

@@ -17,6 +17,7 @@
 
 - [Email](03-rules_email.md)
 - [Length](03-rules_length.md)
+- [PasswordStrength](03-rules_password-strength.md)
 - [URL](03-rules_url.md)
 
 ## Comparison Rules

docs/03-rules_password-strength.md

@@ -0,0 +1,60 @@
+# PasswordStrength
+
+Validates that the given password has reached the minimum strength required by the constraint. 
+The strength is calculated by measuring the entropy of the password (in bits) based on its length and the number of unique characters.
+
+```php
+PasswordStrength(
+    string $minStrength = 'medium', 
+    ?string $minMessage = null
+);
+```
+
+## Basic Usage
+
+```php
+Validator::passwordStrength()->validate('password'); // false
+Validator::passwordStrength()->validate('i8Kq*MBob~2W"=p'); // true
+Validator::passwordStrength(minStrength: 'very-strong')->validate('i8Kq*MBob~2W"=p'); // false
+```
+
+> [!NOTE]
+> An `UnexpectedValueException` will be thrown when a `minStrength` option is invalid.
+
+> [!NOTE]
+> An `UnexpectedValueException` will be thrown when the input value is not a `string`.
+
+## Options
+
+### `minStrength`
+
+type: `string` default: `medium`
+
+Sets the minimum strength of the password in entropy bits.
+The entropy is calculated using the formula [here](https://www.pleacher.com/mp/mlessons/algebra/entropy.html).
+
+Available options are:
+
+- `weak` entropy between `64` and `79` bits.
+- `medium` entropy between `80` and `95` bits.
+- `strong` entropy between `96` and `127` bits.
+- `very-strong` entropy greater than `128` bits.
+
+All measurements less than `64` bits will fail.
+
+### `message`
+
+type: `?string` default: `The password strength is not strong enough.`
+
+Message that will be shown when the password is not strong enough.
+
+The following parameters are available:
+
+| Parameter           | Description               |
+|---------------------|---------------------------|
+| `{{ name }}`        | Name of the invalid value |
+| `{{ minStrength }}` | Selected minimum strength |
+
+## Changelog
+
+- `0.8.0` Created