readme updates according to issues

subjects/btreetransplant/README.md

@@ -30,8 +30,8 @@ func main() {
 	piscine.BTreeInsertData(root, "7")
 	piscine.BTreeInsertData(root, "5")
 	node := piscine.BTreeSearchItem(root, "1")
-	replacement := &piscine.TreeNode{Data: "3"}
-	root = piscine.BTreeTransplant(root, node, replacement)
+	rplc := &piscine.TreeNode{Data: "3"}
+	root = piscine.BTreeTransplant(root, node, rplc)
 	piscine.BTreeApplyInorder(root, fmt.Println)
 }
 ```

subjects/social-network/README.md

@@ -218,6 +218,9 @@ Every other notification created by you that isn't on the list is welcomed too.
 - [golang-migrate](https://github.com/golang-migrate/migrate/)
 - [sql-migration](https://pkg.go.dev/github.com/rubenv/sql-migrate)
 - [migration](https://pkg.go.dev/github.com/Boostport/migration)
+- [sqlite3](https://github.com/mattn/go-sqlite3)
+- [bcrypt](https://pkg.go.dev/golang.org/x/crypto/bcrypt)
+- [UUID](https://github.com/satori/go.uuid)
 
 This project will help you learn about:
 

subjects/ztail/README.md

@@ -18,8 +18,11 @@ If `file1.txt` & `file2.txt` contains :
 
 ```
 abcdefghijklmnopqrstuvwxyz
+
 ```
 
+**Note** that the files above end with a new line.
+
 Normal cases :
 
 ```