Update basic usage

docs/basic-usage/basic-usage.md

@@ -49,3 +49,40 @@ Settings::isFalse('app.debug'); // false
 Settings::set('app.debug', false);
 Settings::isFalse('app.debug'); // true
 ```
+
+## Retrieve all settings
+
+Using `all`, you can retrieve all the stored settings, which will be returned as a collection. You may also retrieve a subset of settings
+by passing in an array of keys to retrieve.
+
+```php
+Settings::all();
+
+// Subset of settings
+Settings::all(['foo', 'bar']);
+```
+
+The collection of settings returned from this method will contain objects structured like this:
+
+```json
+{
+    "id": 1,
+    "key": "foo",
+    "value": "bar",
+    "original_key": "foo"
+}
+```
+
+> {info} The `original_key` property is set by settings to reflect the key that is used in the database.
+
+## Flushing settings
+
+Multiple settings can be deleted at one time using the `flush` method on settings. It works similar to `forget`, however
+it is not able to flush the cache for each setting, unless you pass in a subset of keys to flush.
+
+```php
+Settings::flush();
+
+// Flush a subset of settings
+Settings::flush(['foo', 'bar']);
+```