Add possibility to switch color schemes

[denolia]

I would love to be able to use another color schemes: e.g. from blue to red or from blue to purple.

• One of the options is to add an arg option e.g.

mvn clean install | cpucat --colors blue red 

or with hex:

mvn clean install | cpucat --colors "#ffffff" "#ff0000" 

• Another option is to add a global setting that needs to be set only once

cpucat --set-colors  "#ffffff" "#ff0000" 

and from now on all executions will use these color settings.

[samoylovfp]

In case it is decided to go with the global config I suggest looking at
https://lib.rs/crates/dirs
or
https://lib.rs/crates/directories