Optimizing for size: update list of modules that can be disabled

Add comment explaining that this is not magic, users should review the list.

development/compiling/optimizing_for_size.rst

@@ -56,7 +56,12 @@ a lot of them:
 
 ::
 
-    scons p=windows target=release tools=no module_bmp_enabled=no module_bullet_enabled=no module_csg_enabled=no module_dds_enabled=no module_enet_enabled=no module_etc_enabled=no module_gdnative_enabled=no module_gridmap_enabled=no module_hdr_enabled=no module_mbedtls_enabled=no module_mobile_vr_enabled=no module_opus_enabled=no module_pvr_enabled=no module_recast_enabled=no module_regex_enabled=no module_squish_enabled=no module_tga_enabled=no module_thekla_unwrap_enabled=no module_theora_enabled=no module_tinyexr_enabled=no module_vorbis_enabled=no module_webm_enabled=no module_websocket_enabled=no
+    scons p=windows target=release tools=no module_arkit_enabled=no module_assimp_enabled=no module_bmp_enabled=no module_bullet_enabled=no module_camera_enabled=no module_csg_enabled=no module_dds_enabled=no module_enet_enabled=no module_etc_enabled=no module_gdnative_enabled=no module_gridmap_enabled=no module_hdr_enabled=no module_jsonrpc_enabled=no module_mbedtls_enabled=no module_mobile_vr_enabled=no module_opensimplex_enabled=no module_opus_enabled=no module_pvr_enabled=no module_recast_enabled=no module_regex_enabled=no module_squish_enabled=no module_svg_enabled=no module_tga_enabled=no module_theora_enabled=no module_tinyexr_enabled=no module_upnp_enabled=no module_vhacd_enabled=no module_vorbis_enabled=no module_webm_enabled=no module_webp_enabled=no module_webrtc_enabled=no module_websocket_enabled=no module_xatlas_unwrap_enabled=no
+
+If this proves not to work for your use case, you should review the list of
+modules and see which ones you actually still need for your game (e.g. you
+might want to keep networking-related modules, regex support, or theora/webm
+to play videos).
 
 Optimizing for size instead of speed
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