LibGfx: Add the ability to append a Path into another

This is useful in general (I'd imagine), but in particular having this
will allow us to implement accented PDF Type1 Font glyphs, which consist
of two separate glyphs that are composed into a single one.

Userland/Libraries/LibGfx/Path.h

@@ -243,6 +243,14 @@ public:
         return m_bounding_box.value();
     }
 
+    void append_path(Path const& path)
+    {
+        m_segments.ensure_capacity(m_segments.size() + path.m_segments.size());
+        for (auto const& segment : path.m_segments)
+            m_segments.unchecked_append(segment);
+        invalidate_split_lines();
+    }
+
     Path copy_transformed(AffineTransform const&) const;
 
     DeprecatedString to_deprecated_string() const;