fix(theme): add missing methods

fix #50

Author: gaetan-hexadog

src/Theme.php

@@ -140,6 +140,11 @@ public function setVersion(string $version): self
         return $this;
     }
 
+    public function getVersion(): string
+    {
+        return $this->version;
+    }
+
     /**
      * Set theme description.
      */
@@ -150,6 +155,11 @@ public function setDescription(string $description): self
         return $this;
     }
 
+    public function getDescription(): string
+    {
+        return $this->description;
+    }
+
     /**
      * Set theme name.
      */