Fix print of block string with leading space and quotation

[IvanGoncharov]

When I looked at #1188 I noticed that current implementation doesn't handle strings like that:

"""    space-led value "quoted string"
"""

Currently it's printed as:

"""    space-led value "quoted string""""
                                     ^ breaks parser

[IvanGoncharov]

Can be replaced with:

return maybeString && maybeString.replace(/^|\n/g, '$&  ');

But I chose easier to read version even those it's more verbose.

[leebyron]

What do you think about just simplifying block string printing to always be:

"""
Content
"""

That would require updating some test cases, but would be much more predictable

[IvanGoncharov]

What do you think about just simplifying block string printing to always be:

@leebyron I'm confused 😕
If you transform """ space-led""" into:

""""
   space-led
"""

You would lose prefix spaces.
Or do you want to change the specification to remove leading and trailing spaces from block string?

[leebyron]

Great question about that edge-case. Let me look into that and return to a decision soon

[leebyron]

Let's stick with this approach, nice work