Support multi-dollar interpolation

[rocketraman]

When using the new experimental multi-dollar interpolation feature, ktfmt appears to bork with the error:

Step 'ktfmt' found problem in 'MyFile.kt':
104:35: error: Expecting an expression
com.facebook.ktfmt.format.ParseError: 104:35: error: Expecting an expression
        at com.facebook.ktfmt.format.Parser.throwParseError(Parser.kt:71)
        at com.facebook.ktfmt.format.Parser.parse(Parser.kt:65)
        at com.facebook.ktfmt.format.Formatter.sortedAndDistinctImports(Formatter.kt:143)
        at com.facebook.ktfmt.format.Formatter.format(Formatter.kt:90)

I am running it through Gradle+Spotless.