Add heat map data structure

api/src/engine/models/result/heat-map-result.model.ts

+import { Field, ObjectType } from '@nestjs/graphql';
+import { Result } from './common/result.model';
+
+@ObjectType()
+export class HeatMapResult extends Result {
+  @Field()
+  name: string;
+
+  @Field(() => [[Number]])
+  matrix: number[][];
+
+  @Field(() => [String])
+  xLabels: string[];
+
+  @Field(() => [String])
+  yLabels: string[];
+}