math: add missing docstrings for vlib/math functions (#19617)

Author: dotdot0

vlib/math/bits.v

@@ -53,6 +53,7 @@ pub fn is_inf(f f64, sign int) bool {
 	return (sign >= 0 && f > max_f64) || (sign <= 0 && f < -max_f64)
 }
 
+// is_finite returns true if f is finite
 pub fn is_finite(f f64) bool {
 	return !is_nan(f) && !is_inf(f, 0)
 }

vlib/math/complex/complex.v

@@ -12,7 +12,7 @@ pub mut:
 	im f64
 }
 
-// complex returns a complex struct with the given `re`al and `im`aginary parts
+// complex returns a complex struct with the given `re`al and `im`aginary values
 pub fn complex(re f64, im f64) Complex {
 	return Complex{re, im}
 }

vlib/math/invhyp.v

@@ -1,8 +1,8 @@
 module math
 
 import math.internal
-// acosh returns the non negative area hyperbolic cosine of x
 
+// acosh returns the non-negative area hyperbolic cosine of x
 pub fn acosh(x f64) f64 {
 	if x == 0.0 {
 		return 0.0

vlib/math/stats/stats.v

@@ -469,6 +469,9 @@ pub fn skew_mean_stddev[T](data []T, mean T, sd T) T {
 	return skew
 }
 
+// quantile calculates quantile points
+// for more reference 
+// https://en.wikipedia.org/wiki/Quantile
 pub fn quantile[T](sorted_data []T, f T) T {
 	if sorted_data.len == 0 {
 		return T(0)