[Feature] Generate goal from believe containing mental operation Want

[biaktfn]

Is your feature request related to a problem? Please describe

There is a test for NAL-9 as below:

(^want,{SELF},<a --> b>). %1.00;0.90%
10
''outputMustContain('<a --> b>! %1.00;0.81%')

Currently there seems to be some related code but this feature is not implemented yet.