Allow formatting code with a different base level of indentation

[vinistock]

Being able to override the base level of indentation allows us to format parts of a document that may be nested. This will allow the Ruby LSP to implement range formatting.

For example,

class Foo
  def bar # if we select only the bar method definition for formatting, we need to start from indentation level 2
    puts "Hello"
  end
end

The necessary changes in prettier print are here ruby-syntax-tree/prettier_print#4.

Concerns

Currently, the implementation adds the new base indentation to the last new line of the formatted source. For example,

  def foo
    puts "level 2"
  end
   # <-- Two spaces are added after this new line as well

I'm not sure if this is coming from Syntax Tree or prettier print. This is why we currently have the rstrip in the tests.

[kddnewton]

@vinistock whenever you get the chance can you rebase this an use prettierprint v1.2.0? Just released.

[kddnewton]

Update prettier_print dependency