highlight issues "else if" should NOT be legal for spin2

[ironsheep]

Checklist:

• [x] I updated to the latest spin2 version available
• [x] I have restarted VSCode and the problem still exists

Version of Spin2 Extension with the issue: v1.8.8

Last working version (if known): Possible never has worked?

Hardware, Operating System, VSCode version:

Description of problem:

Additional information: (please attach your source file (.spin2) exhibiting the problem you are describing.) The "Else If" in this case should be RED! (illegal). It does NOT compile!

[ironsheep]

Fixes committed and appear in v1.9.0 and later.