Add Support for Loading .bml Manifests

[Awakened0]

It doesn't seem like there is a way to load .bml manifests with the bsnes libretro core. In stand alone bsnes 115, you can simply name the manifest the same as the ROM file and put it in the same folder.

There is at least one ROM hack that requires a manifest to run. Mega Man X3 Zero Project: https://www.romhacking.net/hacks/4086/

And the manifest is here: https://raw.githubusercontent.com/justin3009/MMX3-ZeroProject/master/Mega%20Man%20X3%20Manifest%20%5Bv115%20of%20BSNES!%5D%20%5BRename%20to%20ROM%20name%20in%20same%20ROM%20folder!%5D.bml