Fix not being able to reflow certain blocks

Blocks with identical start and end markers and no line start pattern could not be reflowed if there was a trailing blank line after block end. Encountered this while trying to add support for Python docstrings.

Add support for Visual Studio 2022

Drop support for Visual Studio 2015 and 2013.

Use async initialization in Visual Studio 2015 and above

Async initialization is a requirement for VS2019. Dropped support for VS2012.

Add support for Visual Studio 2019

Verified that it works in Visual Studio 2013, 2015, 2017 and 2019. Have not checked 2012.

Add support for Visual Studio 2017

Support for VS 2013 and/or 2012 might be broken now. I haven't been able to check.

Version 1.1.1

Fixed installation errors for Visual Studio 2012 and Visual Studio 2013 when Visual Studio 2015 is not installed.

Version 1.1.0

Added settings import/export feature from @xMRi.

Version 1.0.1

Updated manifest to support later versions of the .NET Framework.

Version 1.0.0

Initial support for VSIX.