Added twitch to allowed sites to be sanitized

[HyperTHD]

Issue This PR Addresses

This PR closes #2897

Type of Change

• Bugfix: Change which fixes an issue
• New Feature: Change which adds functionality
• Documentation Update: Change which improves documentation
• UI: Change which improves UI

Description

This PR adds twitch to the list of sites that won't be sanitized by our html sanitizer. This should allow for posts that include twitch links to be viewed on telescope posts.

Steps to test the PR

Simply check for any post that contains a twitch video included in their blog post. The most recent one was one by @sirinoks on February 11th, 2022 titled, "Telescope stream"

Checklist

• Quality: This PR builds and passes our npm test and works locally
• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not (if applicable)
• Documentation: This PR includes updated/added documentation to user exposed functionality or configuration variables are added/changed or an explanation of why it does not(if applicable)

[gitpod-io]

[humphd]

Excellent!