fix: incorrect multiline autoindent

[joeljohansson99]

Fixes #1000

Open to suggestions. I feel like there is no very good way of do this. This is the best I could come up with.
If we want to preserve the relative indent, then we would just need to handle the midline paste case.

Let me know what you think

Thanks!

[sebthom]

Thanks for your PR! Can you please add some inline comments and if possible a test case?

[joeljohansson99]

Hi @sebthom. Thanks for the reply!
I added comments and also discovered a potential bug in the process. String.stripLeading() removes newlines as well as whitespaces, which we dont want, so instead I used a regex.

I also added two new test cases. Both which are failing for the old implementation but with this fix are succeding.
With the previous implementation it failed like this:

expected: 
  "public class Foo {
   function bar() {
    
   }
  }"
 but was: 
  "public class Foo {
   function bar() {
     
    }
  }"

And

expected: 
  "public class Foo {
   function foo() {
    if (cond) {
    } else {
    }
   }
  }"
 but was: 
  "public class Foo {
   function foo() {
    if (cond) {
    }   else {
      }
   }
  }"

Let me know if you have any questions! Thanks!