Add getters for docParser/HtmlRenderer/extensions

[dshafik]

These small additions make it much easier to make changes to the parser/renderer/environment (and helps to be able to effectively unit test them a bit better)

Added: made all private elements protected instead, kept running into issues when extending. A concrete example is that I am unable to easily add support for ?[Word](definition) as most of League\CommonMark\Inline\Parser\CloseBracketParser is private.

[colinodell]

I'm against this change, simply because CommonMarkConverter is a stupid-simple convenience wrapper for people who only care about simple conversions of CommonMark.

Anyone needing additional functionality can easily init those classes themselves and do whatever they feel like.

[dshafik]

Why make it more difficult? Also, makes it easier when you think about extensions and the possibility of a factory.

Why should I have to create an environment, docParser and htmlRenderer, when all I want is to change one thing in the htmlRenderer? Instead use this and ->getHtmlRenderer() and go from there.

[colinodell]

when all I want is to change one thing in the htmlRenderer

There's nothing you can really change though - if there was, then I'd be okay with this change.

[colinodell]

I'm closing this in favor of #52 and #53:

• Delay extension initialization #52 includes one of the getters you were looking for. I'd prefer to avoid adding the other unless there's a compelling use-case for them.
• Make some private elements protected instead for easier extending #53 includes the majority of the private -> protected changes. I kept a few things private that I didn't think were necessary to expose. If you disagree, let me know which ones you think should change and why.

Thanks!