Add neoTRNG Documentation to 45GS02 Microprocessor

[lydon42]

Latest development build has neoTRNG functional for the first time. So noiw we need to add some documentation for it.

Add an example how it is used and explain how random neoTRNG numbers are. See src/vhdl/neotrng.vhdl for information and references.

Example of use:

           LDX #$00
rngnotrdy: BIT $D7FE       ; check bit 7 (->N) if RNG is still sampling
           BMI rngnotrdy   ; still sampling, wait...
           LDA $D7EF       ; load random number
           STA $0800,X     ; store to screen...
           DEX
           BNE rngnotrdy   ; do it again