basic nuemark inline span support

[nobkd]

Adds basic support for inline spans:

• hello [.green "*content*"] etc -> hello <span class="green"><em>content</em></span> etc
• hello [.myclass] -> hello <span class="myclass"></span>

this is not really pretty currently (and may not work as expected in some cases), but works for now

to be done:

• inline span support
• other valid inline html tags [i "content"] -> <i>content</i> () (without manual component) (other PR?)
• other valid html block tags for block scope nuemark tags (without manual component) (other PR?)
• maybe doing the last two in nuekit, where you can check, if a custom tag was defined with the same name, and if not use just default html tag?

Note

someone else may take over the other tasks or work more on this, if they want.

[goblinfactory]

Are the quotes entirely necessary?

hello [.green "*content*"] etc -> hello <span class="green"><em>content</em></span> etc

could also be made to work as follows, without requiring quotes

hello [.green *content*] etc -> hello <span class="green"><em>content</em></span> etc

Which is cleaner and easier to read when there might be use cases where a lot of tagging of content in a particular paragraph is required.

[nobkd]

Yes, you need the quotation marks, though you can also use single (') ones. otherwise it would be an html attribute. (though I'm not sure, if it gets rendered.)

If you have e.g. an emphasis around the content, it might work (on single words?), but i wouldn't bet on it.