Update Abyss.tmTheme to color invalid code red fixes #85

[rl-utility-man]

1. This modifies this built in VS Code theme to comply with the red-means-invalid convention implemented in built in VS Code Themes including the Default Dark Default Dark+.
2. This change applies the widely accepted convention that red means stop or danger to invalid code. It also draws a clearer contrast between invalid syntax and routine, valid syntax.