Feature: Allow appending custom html attributes.

[georgeiliadis91]

I believe it would be a good idea to allow the user to choose and append custom attributes to selected html tags.

Anything from class names to attributes.
An example would we allowing the user to set lazy loading on images allowing more control on markdown that is received.

<img loading="lazy .... />"

[heychazza]

+1 would tie in well with #964

[thdoan]

I was going to create a new ticket until I saw this. I think this would allow us to add rel="noopener noreferrer" target="_blank" to specific links.

[XolifyDev]

is this being made?