Add automatic indentation on new lines

[PrimeTimeTran]

When a user hits enter in the editor they expect that the new line has the same indentation as the previous line if I'm not mistaken.

That's not the behavior flutter_code_editor has.

Might we be able to add that?

I appreciate your work so far! I'm using it for seepdeep.com and hope to do so moving forward.

However this issue makes using this lib frustrating.

Thanks again =)

[heckmon]

@PrimeTimeTran I have created a code editor package similar to this with a little more features including auto indentation. Please have a look