fs.php: add filesystem functions

inc/functions/fs.php

@@ -0,0 +1,10 @@
+<?php
+namespace Vichan\Functions\Fs;
+
+
+function link_or_copy(string $from, string $to) {
+	if (!\link($from, $to)) {
+		return \copy($from, $to);
+	}
+	return true;
+}