A section on LCD artifacts may be useful

This would cover things such as blur/smearing/etc, including simple 2-frame blending effects, but also more complex behaviors. One of the more complex behaviors is as follows.

ISSOtm noticed an unexpected artifact in [The Forest Hero](https://geckoball.itch.io/the-forest-hero), as described here:

> Go into the hole shown at the beginning, then go up and down the stairs
My DMG shows a bunch of vertical lines for some reason

Based on the belief that it was due to the brick tiles effectively toggling pixels between black/white on alternating frames I created the following test ROM. If you press A when this ROM is running the stripped tiles will essentially be xor'd every other frame, leading to a similar effect, which gets worse as there's more white in a given column.

It's not quite the same as the game because this is 50:50 white/black, but I believe it's the same effect.

(**FLASHING WARNING: You probably don't want to press A with this ROM without frame blending enabled in an emulator, as it will flash very quickly.**):
[vertical_smear.zip](https://github.com/gbdev/pandocs/files/7824817/vertical_smear.zip)

LIJI produced mockups of the resulting effect on their GB Light with normal contrast:


as well as high contrast:

I'm unaware of an emulator which attempts to emulate this behavior at this time.

Start with the issue body, the linked vertical_smear.zip test ROM, and the cited Forest Hero reproduction steps. Establish which LCD artifacts are in scope, then document the observed smear and blending behavior with appropriate flashing warnings; done means the proposed LCD-artifacts section is complete and technically grounded.

Written by the indexing model from the issue text.