0.22.0: Syntax Tree Ornament

Breaking

• SourceKitten now requires Swift 4.2 or higher to build.
  JP Simard

Enhancements

• Add Request.syntaxTree to get a serialized representation of the file's
  SwiftSyntax tree.
  JP Simard

Bug Fixes

• Fix crash in NSString.location(fromByteOffset:) when using unicode
  characters.
  JP Simard
  realm/SwiftLint#2276