go: add «2873. Maximum Value of an Ordered Triplet I»

URL:	https://leetcode.com/problems/maximum-value-of-an-ordered-triplet-i/
Signed-off-by: Matej Focko <me@mfocko.xyz>

go/maximum-value-of-an-ordered-triplet-i.go

@@ -0,0 +1,14 @@
+package main
+
+func maximumTripletValue(nums []int) int64 {
+	var maxValue, imax, dmax int64 = 0, 0, 0
+	for _, x := range nums {
+		num := int64(x)
+
+		maxValue = max(maxValue, dmax*num)
+		dmax = max(dmax, imax-num)
+		imax = max(imax, num)
+	}
+
+	return maxValue
+}