feat(#129): add iCal response parser

app/Services/Plugin/Parsers/ResponseParser.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace App\Services\Plugin\Parsers;
+
+use Illuminate\Http\Client\Response;
+
+interface ResponseParser
+{
+    /**
+     * Attempt to parse the given response.
+     *
+     * Return null when the parser is not applicable so other parsers can run.
+     */
+    public function parse(Response $response): ?array;
+}