U 21 diff (#23)

* add logo and fix project image description

* add difference function

* update docs

Co-authored-by: Ruidy <rnemausat@newstore.com>

README.md

@@ -4,7 +4,7 @@
 ![Go version](https://img.shields.io/github/go-mod/go-version/rjNemo/underscore?style=for-the-badge)
 ![test coverage](https://img.shields.io/codecov/c/github/rjNemo/underscore?style=for-the-badge)
 
-![underscore](https://socialify.git.ci/rjNemo/underscore/image?description=1&descriptionEditable=Useful%20functional%20programming%20helpers%20for%20Go%201.18%20and%20beyond&font=Raleway&language=1&logo=https%3A%2F%2Fgithub.com%2FrjNemo%2Funderscore%2Fblob%2Fmain%2Fdocs%2Fstatic%2Flogo.png&owner=1&pattern=Floating%20Cogs&stargazers=1&theme=Light)
+![underscore](https://socialify.git.ci/rjNemo/underscore/image?description=1&descriptionEditable=Useful%20functional%20programming%20helpers%20for%20Go%201.18%20and%20beyond&font=Raleway&language=1&logo=https%3A%2F%2Fraw.githubusercontent.com%2FrjNemo%2Funderscore%2Fmain%2Fdocs%2Fstatic%2Flogo.png&owner=1&pattern=Floating%20Cogs&stargazers=1&theme=Light)
 
 `underscore` is a `Go` library providing useful functional programming helpers without extending any built-in objects.
 

difference.go

@@ -0,0 +1,8 @@
+package underscore
+
+// Difference Returns a copy of the array with all instances of the values that are not present in the other array.
+func Difference[T comparable](slice, other []T) []T {
+	return Filter(slice, func(n T) bool {
+		return !Contains(other, n)
+	})
+}

difference_test.go

@@ -0,0 +1,17 @@
+package underscore_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	u "github.com/rjNemo/underscore"
+)
+
+func TestDifference(t *testing.T) {
+	nums := []int{1, 3, 5, 6, 7, 9}
+	reject := []int{9, 7, 5, 4}
+	want := []int{1, 3, 6}
+
+	assert.Equal(t, want, u.Difference(nums, reject))
+}

docs/content/collections/difference.md

@@ -0,0 +1,22 @@
+---
+title: "Difference"
+date: 2022-03-21T13:48:21-04:00
+---
+
+Returns a copy of the array with all instances of the values that are not present in the other arrays.
+
+```go
+package main
+
+import (
+	"fmt"
+	u "github.com/rjNemo/underscore"
+)
+
+func main() {
+	nums := []int{1, 3, 5, 6, 7, 9}
+	reject := []int{9, 7, 5, 4}
+	
+	fmt.Println(u.Difference(nums, reject)) // {1, 3, 6}
+}
+```