Add conference collection to the CMS config

[deweydell]

Description

For each conference, we want to be able to create a new collection of content. Each year we'll be able to create a new conference page in the CMS by clicking a New Conference button and filling out the information.

Adding content about the 2019 conference is out of scope of this issue, this is just to add the configuration to the CMS.

Acceptance Criteria

In the CMS:

• Conferences is a collection in the sidebar
• You are able to create a New Conference
• You are not able to delete conferences from the CMS
• Conferences have the settings below (for now)
• Year: Number (required)
• Start Date: Date
• End Date: Date
• City, State: String
• Hotels: list of objects (see Netlify Widgets documentation)

Each hotel object will have:

• Name: string
• Address: string
• Room Rate: string
• Reservation Link: string
• Phone: string
• Group name: string

Resources

Netlify CMS Configuration in docs:
https://www.netlifycms.org/docs/widgets/