Support completion in template strings using `

[ModProg]

closes #467

[bradlc]

Please see #465 (comment)

[ModProg]

For anyone coming across this needing this as regex you can use:

'(?:classes|class)\\s*=\\s*`([^`]*)',

Replace classes|class with all the variable names you want to use.

Still would have considered this a small enough change to be added in the code IMO.