SystemVerilog 2.18.0 Changelog:

## Enhancement ##
  - Covergroup :
    * Fix a few highlight issue (and add corresponding tests)
    * Add Snippet for covergroup
    * Add autocompletion specific to covergroup block and option.*
  - Constraint :
    * Improve snippet
    * Add autocompletion specific to constraint
  - Misc:
    * Add highlight for interconnect and untyped

