[web] Updates to the landing page

[jonxuxu]

Ticket	Title
fixes #41	[web] Embed Myriade Explainer Video in homepage
fixes #40	[web] change date in footer
fixes #39	[web] Update Discord invite link in footer

Description

As per @sqphoenix 's request, this PR does the following:

• Adds video to landing page
• Updates year and Discord link in footer

In addition, this PR updated the spacing between website sections, and put the mailing list form in a Jumbotron.

Screenshots