Added `themeColor` meta tag to support Discord Embed & mobile Chrome Browsers

[schwarzsky]

Description of Change(s):

Added themeColor meta tag to support Discord Embed & mobile Chrome Browsers.

In chrome, changes search bar color as MDN Docs shows: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta/name/theme-color

In Discord, changes embeds left bar color by themeColor meta: https://stackoverflow.com/questions/54266598/meta-tags-for-url-with-description-and-image-in-skype-discord

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To help get PR's merged faster, the following is required:

• [x] Updated the documentation
• [x] Unit/Cypress test covering all cases

Please link to relevant Google Docs or schema.org docs for what you are adding so we can review: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meta/name/theme-color