feat: nanoid type

[nguyenkhavi]

• [x] Do only one thing
• [x] Non breaking API changes
• [x] Tested

What did this pull request do?

• It's boring to repeatedly create a BeforeCreate hook for each model to generate nanoid automatically.
• So I made a simple and lighweight nanoid data type and hope it could be contributed.

User Case Description

import "gorm.io/datatypes"

type UserWithNanoID struct {
    ID   datatypes.NanoID `gorm:"nanoid" json:"id"`
    Name string
}

//Create
user := UserWithNanoID{Name: "nkvi.dev"}
DB.Create(&user)

//Query
result := UserWithNanoID{}
if err := DB.First(&result, "id = ?", user.ID).Error; err != nil {
    t.Fatalf("Failed to find user with id")
}

[quyvm]

Very helpful 👍

[jinzhu]

looks great, but seems it is better to be a independent package?