Add basic framework

src/Puzzle.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace AdventOfCode21;
+
+use AdventOfCode21\Utils\SymfonyConsoleMarkdown;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class Puzzle extends Command
+{
+    protected function configure(): void
+    {
+        $this
+            ->setName('puzzle')
+            ->addArgument('day', InputArgument::REQUIRED, 'The day number.');
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $contents = file_get_contents(sprintf('%s/../data/day%s/puzzle.md', __DIR__, (int) $input->getArgument('day')));
+        $rendered = (new SymfonyConsoleMarkdown())->render($contents);
+
+        $output->writeln($rendered);
+
+        return Command::SUCCESS;
+    }
+}