Make the priority flag description clearer by explicitly referring to "color IDs" instead of "colors"

[RaoulLuque]

When reading the description of byte 3 in the OAM section and more precisely, the priority flag, I was confused whether the sentence
"Priority: 0 = No, 1 = BG and Window colors 1–3 are drawn over this OBJ"
was referring to colors, as in actual colors values (0: White, ...) or whether it was referring to color IDs (which might be mapped by the palette to other color values then their ID might suggest). I suppose it refers to color IDs, which is why I would make that more explicit.

If that is wrong I would suggest changing it to make it clear that color IDs are not meant and instead color values. I was not able to find a conclusive source on this.

Note that the link that is used for the color IDs is the same as used in the palettes section.

[ISSOtm]

Thank you for the contribution! It does indeed refer to colour IDs, your guess was correct!

Would you mind checking the corresponding flag in the BG attributes description (Tile_Maps.md)? I believe it's more or less a copy-paste.

[avivace]

If we go for this nomenclature change, there are some usages of "Color IDs" in src/Graphics.md as well

[RaoulLuque]

Good catch, I'll search for more occurrences and change all of them accordingly 👍