Add feature table entry for new dynamic media API

builtin/game/features.lua

@@ -21,6 +21,7 @@ core.features = {
 	use_texture_alpha_string_modes = true,
 	degrotate_240_steps = true,
 	abm_min_max_y = true,
+	dynamic_add_media_table = true,
 }
 
 function core.has_feature(arg)

doc/lua_api.txt

@@ -4567,6 +4567,8 @@ Utilities
           degrotate_240_steps = true,
           -- ABM supports min_y and max_y fields in definition (5.5.0)
           abm_min_max_y = true,
+          -- dynamic_add_media supports passing a table with options (5.5.0)
+          dynamic_add_media_table = true,
       }
 
 * `minetest.has_feature(arg)`: returns `boolean, missing_features`