Add rel="noreferrer noopener" to external links

[ulmemxpoc]

Related to https://github.com/iv-org/invidious/issues/4297. CC: @SamantazFox.

Adds rel="noreferrer noopener" to constant YouTube links on Invidious frontend. ~~Also change to YT_URL.~~

Does not add rel="noreferrer noopener" to:

• links in channel description
• links in video descriptions
• links in video comments

[ulmemxpoc]

@SamantazFox applied suggested fixes. Please re-review.

[SamantazFox]

Thanks for contributing to invidious :D