feat: add new methods

Exists and getFilepath methods were added.
The file is no longer created if it does not exist when the instance is created.
The $content parameter of the set method is now optional and contains an empty array by default.

Closes #22

Author: josantonius

src/Json.php

@@ -43,6 +43,14 @@ public function exists(): bool
         return $this->isUrl ? @file_get_contents($filepath) !== false : file_exists($filepath);
     }
 
+    /**
+     * Get the path or URL of the JSON file.
+     */
+    public function filepath(): string
+    {
+        return $this->filepath;
+    }
+
     /**
      * Get the content of the JSON file or a remote JSON file.
      *
@@ -54,14 +62,6 @@ public function get(): array
         return $this->getFileContents();
     }
 
-    /**
-     * Get the path or URL of the JSON file.
-     */
-    public function getFilepath(): string
-    {
-        return $this->filepath;
-    }
-
     /**
      * Set the content of the JSON file.
      *