fix: no markdown support for underline #2072

[regevbr]

fix: #2072
Add support for underline in markdown by using ++underline++.
This fix will also show up in the editor

[NGPixel]

2 things to improve:

• Make it optional by adding a toggle as part of the Markdown Core module. Since this is not compliant with the CommonMark specification, it shouldn't be mandatory.

• Avoid adding a new npm dependency for just 10 lines of code. Include the code directly.

[regevbr]

Thanks @NGPixel for the comments.

I didn't use the library I mentioned in the issue as it will conflict with the current behavior of _sdf_ so I used a different one - markdown-it-plugin-underline which I can't locate its repository but it is a bit more complicated and contains 120 lines of code. So I don't think in-lining it will make sense.

About the toggle, I will add it

[regevbr]

Done, can you please review?

[NGPixel]

Just not a fan of including an npm module with no public source available.

I think it would be more convenient and intuitive to use the _word_ syntax, which the other module does.

[regevbr]

Ok, but itwill collide with current behavior causing change of ui for existing pages. If you are ok with it, I will be happy to do it

[NGPixel]

That's fine. It's an optional feature that can be turned off and almost everyone is using the *word* syntax for italic already. _word_ is simply more intuitive as underline for everybody.

[regevbr]

@NGPixel I fixed it like you suggested, but I found myself duplicating the plugin code in both server and client. Is there a better way for it? (using the npm package is one way but you said you prefer not to)

[NGPixel]

Yeah it's not ideal for now, but the goal is to use the server pipeline in the future, eliminating the need to duplicate everything on the client.

[regevbr]

Thanks for the review and merge!