Banner Updates for Forum 2.0

[kosmostasis]

This issue is to make the following changes to the Forum banner following the Example image below:

• Change the banner's font to Proto Mono.zip.
• Change the background image to the one included below:

• Change the forum logo to the one included below (and maintain the link to iotex.io if possible):

• Change the call-to-action of the green button's text to "GET STARTED WITH THE FORUM" and delete the current link. The new link is: https://iotex.io/blog/welcome-iotex-forum/

• Change the icons under "Follow Us" to green icons.zip. Links are: Twitter, Discord, YouTube, Reddit, Telegram, GitHub.

• After updating the icons, delete "→ Github" from under "Learn More".