AK: Add {Little,Big}Endian::bytes()

This allows you to easily convert those types to ReadonlyBytes.

AK/Endian.h

@@ -65,6 +65,8 @@ public:
 
     constexpr operator T() const { return convert_between_host_and_little_endian(m_value); }
 
+    constexpr ReadonlyBytes bytes() const { return { this, sizeof(*this) }; }
+
 private:
     T m_value { 0 };
 };
@@ -81,6 +83,8 @@ public:
 
     constexpr operator T() const { return convert_between_host_and_big_endian(m_value); }
 
+    constexpr ReadonlyBytes bytes() const { return { this, sizeof(*this) }; }
+
 private:
     T m_value { 0 };
 };