feat: added NotBlank rule documentation

Author: andrepimpao

docs/03-rules-not-blank.md

@@ -0,0 +1,46 @@
+# NotBlank
+
+Validates that a value is not equal to a blank string, blank array, `false` or `null`.
+
+## Basic Usage
+
+Bellow are the only cases where the rule will fail, everything else is considered valid 
+(you may want to check the [`normalizer`](#normalizer) option for a different behaviour):
+
+```php
+Validator::notBlank()->validate(''); // false
+Validator::notBlank()->validate([]); // false
+Validator::notBlank()->validate(false); // false
+Validator::notBlank()->validate(null); // false
+```
+
+## Options
+
+### `normalizer`
+
+type: `callable` default: `null`
+
+Allows to define a `callable` that will be applied to the value before checking if it is valid.
+
+For example, use `trim`, or pass your own function, to now allow a string with whitespaces only:
+
+```php
+// Existing PHP callables
+Validator::notBlank(normalizer: 'trim')->validate(' '); // false
+
+// Function
+Validator::notBlank(normalizer: fn($value) => trim($value))->validate(' '); // false
+```
+
+### `message`
+
+type: `string` default: `The "{{ name }}" value should not be blank, "{{ value }}" given.`
+
+Message that will be shown if the value is blank. Check the [Custom Messages]() section for more information.
+
+The following parameters are available:
+
+| Parameter     | Description                       |
+|---------------|-----------------------------------|
+| `{{ value }}` | The current invalid value         |
+| `{{ name }}`  | Name of the value being validated |