merge: Add Twin Primes algorithm (#1024)

* Create TwinPrime.js

* Update TwinPrime.js

* Create TwinPrime.test.js

* Update TwinPrime.js

* Update TwinPrime.js

* Add suggestions

* Update TwinPrime.test.js

* Update TwinPrime.js

* Styling

Maths/TwinPrime.js

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+import { PrimeCheck } from './PrimeCheck'
+
+/**
+ * @function twinPrime
+ * Gets the 'twin prime' of a prime number.
+ *
+ * @param {Integer} n The number to find the twin prime of.
+ * @returns {Integer} Either the twin, or -1 if n or n + 2 is not prime.
+ *
+ * @see https://en.wikipedia.org/wiki/Twin_prime
+ *
+ * @example twinPrime(5) = 7
+ * @example twinPrime(4) = -1
+*/
+function twinPrime (n) {
+  const prime = PrimeCheck(n)
+
+  if (!prime) {
+    return -1
+  }
+
+  if (!PrimeCheck(n + 2)) {
+    return -1
+  }
+
+  return n + 2
+}
+
+export { twinPrime }

Maths/test/TwinPrime.test.js

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+import { twinPrime } from '../TwinPrime.js'
+
+describe('Twin Primes', () => {
+  it('Should be valid twin primes', () => {
+    expect(twinPrime(3)).toBe(5)
+    expect(twinPrime(5)).toBe(7)
+    expect(twinPrime(4)).toBe(-1)
+    expect(twinPrime(17)).toBe(19)
+  })
+})