Replace MarkdownExtra with CommonMark

[TomasVotruba]

• more up-to-date
• less wtf
• see: Markdown option #290

Related issues:

• Stale <p> in parameter descriptions #543
• <code> tags are converted to <pre> in the output #426
• Different styling for different class descriptions #541

[miclf]

Hello @TomasVotruba,

Since you decided to switch to the Markdown format, why not take the extra step and use the standard and well-specified Markdown flavor that the community has been working on in the recent months? I’m of course talking of CommonMark.

The PHP League has an actively maintained package to handle it: league/commonmark. It’s following the specification as closely as possible. Which is really nice, because it means we finally have a hope to end the total mess that Markdown has become in the past few years because of the dozens of different flavors that have been built.

[fprochazka]

👍 for CommonMark. The league package looks nice.

[TomasVotruba]

Seems solid. PR with CommonMark is appreciated.

[TomasVotruba]

@jadb Please reopen as new owner. It's not mine issue anymore and I want those remove out of my active issues board.