[TASK] Deprecate DeclarationBlock::expandShorthands (#558)

The `expandShorthands`/`createShorthands` functions are deprecated and
will be removed without substitution in version 10.0.  Expanding and
creating the shorthand notation is out of the scope of this library.

Signed-off-by: Daniel Ziegenberg <daniel@ziegenberg.at>

Author: ziegenberg

CHANGELOG.md

@@ -18,6 +18,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Deprecated
 
+- Deprecate `DeclarationBlock::expandShorthands()` (#558)
+
 ### Removed
 
 - Remove `DeclarationBlock::setSelector()` (#560)

src/RuleSet/DeclarationBlock.php

@@ -169,6 +169,8 @@ public function getSelectors()
      * Splits shorthand declarations (e.g. `margin` or `font`) into their constituent parts.
      *
      * @return void
+     *
+     * @deprecated This will be removed without substitution in version 10.0.
      */
     public function expandShorthands()
     {