Any custom file extension can be associated with standard syntax highlighting with
custom files association
in User Settings as follows.
Note that this will be a permanent setting. In order to set for the current session alone, type in the preferred language in
Select Language Mode
box (without changingfile association
settings)
If the required syntax package is not available by default, you can add them via the Extension Marketplace (Ctrl+Shift+X) and search for the language package.
You can further reproduce the above steps to map the file extensions with the new syntax package.