refactor: constructors, update docs

- NewCustomTable -> NewCustom
- NewTableBy -> NewBy
- NewTable -> New

doc_example_test.go

@@ -8,7 +8,7 @@ import (
 )
 
 func Example_basic() {
-	table := cuckoo.NewTable[int, string]()
+	table := cuckoo.New[int, string]()
 
 	if err := table.Put(1, "Hello, World!"); err != nil {
 		fmt.Println("Put error:", err)