Add docs for interface-over-type-literal (#2170)
Add docs for interface-over-type-literal (#2170)

Add rationale and example for interface-over-type-literal
andy-ms/tslint,berickson1/tslint,mprobst/tslint,berickson1/tslint,IllusionMH/tslint,JoshuaKGoldberg/tslint,andy-ms/tslint,IllusionMH/tslint,palantir/tslint,palantir/tslint,JoshuaKGoldberg/tslint,RyanCavanaugh/tslint,andy-hanson/tslint,RyanCavanaugh/tslint,palantir/tslint,RyanCavanaugh/tslint,berickson1/tslint,andy-hanson/tslint,andy-ms/tslint,mprobst/tslint,mprobst/tslint,andy-hanson/tslint,JoshuaKGoldberg/tslint,IllusionMH/tslint