Add docstrings

Author: namannimmo10

src/runtime/random.py

@@ -1,13 +1,19 @@
 from ltypes import i32, f64, ccall
 
 def random() -> f64:
+    """
+    Returns a random floating point number in the range [0.0, 1.0)
+    """
     return _lfortran_random_float()
 
 @ccall
 def _lfortran_random_float() -> f64:
     pass
 
 def randint(lower: i32, upper: i32) -> i32:
+    """
+    Return a random integer N such that `lower <= N <= upper`.
+    """
     return _lfortran_random_int(lower, upper)
 
 @ccall