docs: Mention some flags in the transition manual
* - | ::lyd_new_opaq() | ^
* - | ::lyd_new_opaq2() | ^
* - | ::lyd_new_path2() | Supplement functionality to ::lyd_new_path().
+ * LYD_PATH_OPT_NOPARENTRET | ::lyd_new_path2() | ::lyd_new_path2() returns both the first parent and the wanted node.
+ * LYD_PATH_OPT_EDIT | ::LYD_NEW_PATH_OPAQ | This functionality was replaced by opaq nodes.
* - | ::lyd_new_ext_path() | Supplement functionality to ::lyd_new_path() covering data defined in extension instances.
* lyd_insert() | ::lyd_insert_child() | Renamed to better distinguish from ::lyd_insert_sibling().
* lyd_change_leaf() | ::lyd_change_term() | Align naming with changed names of data structures.
