Add Ruby snippet for checking prime numbers

Author: ACR1209

snippets/ruby/math-and-numbers/check-prime-number.md

@@ -0,0 +1,21 @@
+---
+title: Check Prime Number
+description: Checks if a number is a prime number.
+author: ACR1209
+contributors: dostonnabotov
+tags: ruby,math,prime,check
+---
+
+```rb
+def is_prime?(n)
+    return false if n <= 1
+    (2..Math.sqrt(n)).each do |i|
+        return false if n % i == 0
+    end
+    true
+end
+
+# Usage:
+puts is_prime?(29) # Output: true
+puts is_prime?(30) # Output: false
+```