Backtracking capable inlines better expressed by interface

src/Components/BacktrackingInline.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Erusev\Parsedown\Components;
+
+use Erusev\Parsedown\Parsing\Excerpt;
+
+interface BacktrackingInline extends Inline
+{
+    /**
+     * Return an integer to declare that the inline should be treated as if it
+     * started from that position in the excerpt given to static::build.
+     * Return null to use the excerpt offset value.
+     * @return int|null
+     * */
+    public function modifyStartPositionTo();
+}