refactor: add php_codesniffer to define castopod's coding style based on psr-1

- add .editorconfig file
- format all files to comply with castopod's coding style
- switch parsedown dependency with commonmark library to better follow commonmark spec for markdown
- add prettier command to format all project files at once

closes #16

tests/_support/Models/ExampleModel.php

@@ -4,23 +4,17 @@ use CodeIgniter\Model;
 
 class ExampleModel extends Model
 {
-	protected $table      = 'factories';
-	protected $primaryKey = 'id';
+    protected $table = 'factories';
+    protected $primaryKey = 'id';
 
-	protected $returnType     = 'object';
-	protected $useSoftDeletes = false;
+    protected $returnType = 'object';
+    protected $useSoftDeletes = false;
 
-	protected $allowedFields = [
-		'name',
-		'uid',
-		'class',
-		'icon',
-		'summary',
-	];
+    protected $allowedFields = ['name', 'uid', 'class', 'icon', 'summary'];
 
-	protected $useTimestamps = true;
+    protected $useTimestamps = true;
 
-	protected $validationRules    = [];
-	protected $validationMessages = [];
-	protected $skipValidation     = false;
+    protected $validationRules = [];
+    protected $validationMessages = [];
+    protected $skipValidation = false;
 }