Add role parameters to support new gradient and holographic roles

[makerze]

Summary

Add new role parameters primary_color, secondary_color and tertiary_color to support new gradient and holographic roles

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)

[DA-344]

Maybe relevant : https://discord.com/channels/336642139381301249/1385146482465837066

[DA-344]

Please, update the corresponding types/ object, and make sure you follow the documentation (pr): discord/discord-api-docs#7549 : only time when colors is not required is when creating a role, but it is still recommended to be passed

[DA-344]

Again, please refer to the discord api docs PR I referred on my last review, these are incorrect.

[DA-344]

Maybe we should change this to not pass the color key on the payload at all, because it is not recommended anymore, use the colors field everytime, even if not using a gradient/holographic colour.

[DA-344]

This and the lines above should just be on colors.primary_color, not on color anymore.

[Rapptz]

This looks fine, just needs the appropriate .. versionadded:: 2.6 strings.

[Rapptz]

Apparently Role.color is now deprecated so you need to get it from Role.colors.primary_color instead. I'm not sure whether it's necessary to do now, but Role.colour should be a property for that and the update route should update primary_color instead.

[DA-344]

LGTM as long as these are fixed!

[DA-344]

LGTM

[Rapptz]

LGTM. Thanks.