LibGfx: Add a function that adds two paths together

This will be used by Path2D#addPath in LibWeb.

Userland/Libraries/LibGfx/Path.cpp

@@ -376,4 +376,10 @@ Path Path::copy_transformed(Gfx::AffineTransform const& transform) const
     return result;
 }
 
+void Path::add_path(Path const& other)
+{
+    m_segments.extend(other.m_segments);
+    invalidate_split_lines();
+}
+
 }

Userland/Libraries/LibGfx/Path.h

@@ -252,6 +252,7 @@ public:
     }
 
     Path copy_transformed(AffineTransform const&) const;
+    void add_path(Path const&);
 
     DeprecatedString to_deprecated_string() const;