Weird ROM sizes

(Related to #106 and #108)

I don't know much about the implementation of anything, but the patterns in the "weird" ROM sizes don't seem that weird to me mathematically:

$05 + $02 -> $52 : 1 MiB + 128 KiB : 64 + 8 banks
$05 + $03 -> $53 : 1 MiB + 256 KiB : 64 + 16 banks
$05 + $04 -> $54 : 1 MiB + 512 KiB : 64 + 32 banks

Start by reading the related issues #106 and #108, then locate the documentation section covering ROM size values. Done should mean the relationships among the $52, $53, and $54 values, capacities, and bank counts are clearly explained.

Written by the indexing model from the issue text.