Add snapshot feature to save diagram as SVG

The Sysl: Save Diagram Snapshot command saves the current diagram editor view as an SVG alongside the Sysl spec that it's rendering. The command can be triggered by a button on the diagram editor title bar.

On save, an information box is displayed with the filename and directory path.

Also:

• Fixed tests on Windows
• Fixed release job in CI (hopefully)
• Tidied up some issues with the package.json, command registration, and tests.

Rudimentary Language Server

1. Added a functionality to use the newly updated language server
2. A few highlighter fixes

Syntax Highlighter Implementation Change

Stabler and syntax highlighter

Add deployment settings

v0.0.7

changed to version 0.0.7 (#24)

Updated Syntax Highlighting

v.0.0.7

add new extension publishing token (#23)