init number dir create listOfIntegers function then write testCases for that function

src/pages/number/generate/service.ts

@@ -0,0 +1,12 @@
+export function listOfIntegers(
+    first_value: number, 
+    number_of_numbers: number,
+    step: number,
+    separator: string) {
+        const result: number[] = [];
+        for (let i: number= 0; i <number_of_numbers; i++) {
+            const value: number = first_value + i * step;
+            result.push(value);
+        }
+        return result.join(separator);
+    }