Version 1.2.0 - Highland release

With the release of A Highland Song behind us, we have a selection of minor updates, fixes and improvements that brings ink to version 1.2.0, otherwise known as the Highland release!

• It’s now possible to have a newline between a choice’s label and its content, which is helpful for laying out verbose looking choices:

    * (say_something_interesting_about_bricklaying)
        "I did have one interesting fact about bricklaying, if you don't mind me spending taking a fair bit of time to lay the groundwork for it."

• Slight API improvements to Ink Lists to make them a little easier to work with on the game side.
• Fix for errors when attempting to load a new version of story during development after major changes (Thanks @russellquinn)
• Fix for choices that were storing thread references in a non-safe way, meaning that it could cause corruption during a background save.
• Fix for choice tags not being serialised (Thanks @hizzz!)
• Fix to allow variable observers to run new ink more robustly by having the callback fire later
• Support for using Continue() to complete a previously active ContinueAsync()
• Runtime is now targeting net standard (Thanks @paulloz!)
• Fix for compiler failing when executed as a process within Unreal Editor 5 (thanks @TCR-Nick!)
• Chinese character ranges now supported for identifiers (thanks @vvjiang!)
• Other minor fixes and improvements (thanks @RobertJaskowski, @Meorge, @dgileadi)