[Website] Add more information on Challenge Mode Rewards to website

[Belodina]

https://www.chromiecraft.com/en/challenge-modes/

Currently, how the rewards system works is not well described on the Challenge Mode page on the website (refer to the image above being the only description of rewards). Adding a description of the reward structure and how to redeem would be beneficial to prevent repeated queries on the discord.

Furthermore, adding pictures of the Tier 3 gear sets and pets/other rewards would also assist readers in choosing to engage with the Challenge Mode System without having to do further research into the rewards and item sets (even if it is quite easy to google).