fix: custom provider generator

[bxcodec]

Proposed changes:
Now we can easily add our own custom faker-generator provider.
Example:

type Gondoruwo struct {
	Name       string
	Locatadata int
}

func CustomGenerator() {
	faker.AddProvider("customIdFaker", func(v reflect.Value) (interface{}, error) {
		 return int64(43), nil
	})
	faker.AddProvider("danger", func(v reflect.Value) (interface{}, error) {
		return "danger-ranger", nil
	})

	faker.AddProvider("gondoruwo", func(v reflect.Value) (interface{}, error) {
		obj := Gondoruwo{
			Name:       "Power",
			Locatadata: 324,
		}
		return obj, nil
	})
}

type Sample struct {
	ID                 int64     `faker:"customIdFaker"`
	Gondoruwo          Gondoruwo `faker:"gondoruwo"`
	Danger             string    `faker:"danger"`
}

Results:

{ID:43 Gondoruwo:{Name:Power Locatadata:324} Danger:danger-ranger}

[codecov]

Codecov Report

Merging #43 into master will decrease coverage by 2.09%.
The diff coverage is 93.97%.

@@            Coverage Diff            @@
##           master      #43     +/-   ##
=========================================
- Coverage   98.12%   96.03%   -2.1%     
=========================================
  Files          10       10             
  Lines         426      529    +103     
=========================================
+ Hits          418      508     +90     
- Misses          4       11      +7     
- Partials        4       10      +6

Impacted Files	Coverage Δ
datetime.go	100% <100%> (ø)	⬆️
uuid.go	100% <100%> (ø)	⬆️
phone.go	100% <100%> (ø)	⬆️
price.go	100% <100%> (ø)	⬆️
payment.go	100% <100%> (ø)	⬆️
address.go	100% <100%> (ø)	⬆️
person.go	97.36% <100%> (-2.64%)	⬇️
internet.go	100% <100%> (ø)	⬆️
lorem.go	100% <100%> (ø)	⬆️
faker.go	89.58% <50%> (-5.88%)	⬇️

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