Register IsBool converter

This commit integrates the IsBool converter into the OTTL function
registry by modifying the `functions.go` file. Specifically, the
function `NewIsBoolFactory[K]()` has been included in the list of
available converters.

The update ensures that the IsBool converter is now available for use
within the existing OTTL framework.

pkg/ottl/ottlfuncs/functions.go

@@ -42,6 +42,7 @@ func converters[K any]() []ottl.Factory[K] {
 		NewFnvFactory[K](),
 		NewHoursFactory[K](),
 		NewIntFactory[K](),
+		NewIsBoolFactory[K](),
 		NewIsMapFactory[K](),
 		NewIsMatchFactory[K](),
 		NewIsStringFactory[K](),