make it more clear what colors are valid in the sample config

[typecasto]

I have no clue how to work the color system, I've tried "#FF9000", "FF9000", and neither of those work. I also tried "orange" and apparently that isn't a color either, so I think it'd be helpful to either give a list of valid colors on the wiki or make one of the segments use a custom color in the sample config.

As an aside, it would also be nice to specify that the config is at ~/.config/silver/silver.toml, I tried ~/.config/silver.toml which didn't work.

[typecasto]

okay I figured out how, it's lowercase letters (ff9000) but I do feel the documentation needs to be better