fix(Twitch): Fix Twitch embed

[MichaelDeBoey]

As announced on their forum, Twitch updated the way the embedded video player is initiated.
This means we now have to pass a parent, which is a list of the domains your content appears on.

BREAKING CHANGE: You'll now need to pass a required parent option whenever you're using the Twitch service
BREAKING CHANGE: Twitch embeds can only be embedded on HTTPS websites. Check out the Gatsby
docs for setting this up when developing locally.

Fixes #128

[codecov]

Codecov Report

Merging #131 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #131   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           16        16           
  Lines          215       220    +5     
  Branches        27        28    +1     
=========================================
+ Hits           215       220    +5     

Impacted Files	Coverage Δ
src/transformers/Twitch.js	100.00% <100.00%> (ø)

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[FabioRosado]

I know I am not a maintainer but the chances look good to me to be honest. It might be worth mentioning that you can use localhost on a non-https site (but again I didn't have much luck with it), but it does make a lot of sense to mention it on the docs.

Also I would like to mention that I like the option for the config, it could also bring some help to other transformers in the future 🤔

[MichaelDeBoey]

🎉 This PR is included in version 3.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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