Add options for deserialization of missing labels

README.md

@@ -58,6 +58,24 @@ Labels correspond to (existing) atoms in Erlang.
 Decoding of a label results in a call to `binary_to_existing_atom/2`, so will
 fail if the corresponding atom does not already exist.
 
+This behavior can be modified using the option `#{missing_labels => fail | create | convert}`,
+where `fail` is the default, as described above, `convert` means that missing atoms are
+converted to binaries, and `create` means that the atom is created dynamically.
+
+The option can be passed e.g.:
+```erlang
+gmser_dyn:deserialize(Binary, set_opts(#{missing_labels => convert}))
+```
+
+or
+```erlang
+gmser_dyn:deserialize(Binary, set_opts(#{missing_labels => convert}, Types))
+```
+
+By calling `gmser_dyn:register_types/1`, after having added options to the type map,
+the options can be made to take effect automatically.
+
+
 It's possible to cache labels for more compact encoding.
 Note that when caching labels, the same cache mapping needs to be used on the
 decoder side.