speglsht.cpp: Add notes

[cam900]

Transparent color is wrong at title screen animation, reference: https://youtu.be/cK7mGnt6YfY?si=Ah5hC_iFS2Li7Xwl

[angelosa]

There are three bugs here by just looking the initial attract sequence:

1. bird's eye view should be circular (sprite?) masked
   
2. example shot shows a grid that is missing
   
3. title screen effectively don't blend the background emblem properly
   

I feel like this should be turned into a task based issue, 2 in particular looks gameplay breaking and in my opinion worth for a MNW demotion.

[mamehaze]

the ball isn't even visible in a lot of situations either.

I kinda agree the issues here are big enough for this to simply be MNW, you wouldn't ship a (legitimate) commercial product with this quality of emulation.