Expose CodeMirror as static property

[sn3p]

As requested in #495 (comment) :)

Unfortunately the CodeMirror object from EasyMDE is not available at that moment, although exposing it on the EasyMDE object should not be difficult (EasyMDE.CodeMirror = CodeMirror; in easymde.js, PR anyone? 😉).

[Ionaru]

As discussed in #495, #514 and similar requests, I cannot guarantee a stable API when exposing CodeMirror or marked. Breaking changed to either package would mean a breaking change in this package. Tree-shaking might break anything from CodeMirror or marked that is used outside the editor.

I think a better option is to implement/expose specific configuration options that users of the editor need to achieve their goals.

[sn3p]

As discussed in #495 ...

You requested to expose it here 😆
But I do understand your concerns, feel free to close this PR.

It's just very frustrating you can't easily load CodeMirror modes before initializing eazyMDE.
Came up with a workaround in #495 (comment).