Registers formatting

Feedback by @Bananattack on [Discord](https://discordapp.com/channels/303217943234215948/666927302348636160/673967141652791298):

> Hmm, I noticed the formatting for registers on the new pandocs is a funky right now:
>
> 1) It's currently inconsistent about whether a hardware register lists its hex address, a symbolic name, or its descriptive "full name". It should probably do all 3, in the order of "hex address - symbolic name - full name"
> 2) LCDC is missing its hex address, and is only called LCD Controller Register in the header.
> 3) Hexadecimal values should probably start with a $ to more clearly call out the numeric base.
> 4) The convention for indicating read/write of a register is inconsistent, sometimes it's (R/W), sometimes it's (Read/Write)

@endrift 's gbdoc (https://github.com/mgba-emu/gbdoc/blob/gh-pages/index.md#mmio) has a very nice way of documenting registers