Separated viewStyle and textStyle keys

[SteveYuOWO]

Fix error of #111 .
In the expo project, a strict type error occurs.

searchBar needs to be strictly defined as TextStyle, and the rest of keys need to be defined as ViewStyle.

✖ tsc --project tsconfig.json --alwaysStrict:
node_modules/react-native-country-codes-picker/index.tsx(271,37): error TS2769: No overload matches this call.
  Overload 1 of 2, '(props: TextInputProps): TextInput', gave the following error.
    Type 'ViewStyle' is not assignable to type 'Falsy | TextStyle | RegisteredStyle<TextStyle> | RecursiveArray<Falsy | TextStyle | RegisteredStyle<TextStyle>> | readonly (Falsy | ... 1 more ... | RegisteredStyle<...>)[]'.
      Type 'ViewStyle' is not assignable to type 'TextStyle'.
        Types of property 'userSelect' are incompatible.
          Type 'string | undefined' is not assignable to type '"text" | "auto" | "none" | "contain" | "all" | undefined'.
            Type 'string' is not assignable to type '"text" | "auto" | "none" | "contain" | "all" | undefined'.
  Overload 2 of 2, '(props: TextInputProps, context: any): TextInput', gave the following error.
    Type 'ViewStyle' is not assignable to type 'Falsy | TextStyle | RegisteredStyle<TextStyle> | RecursiveArray<Falsy | TextStyle | RegisteredStyle<TextStyle>> | readonly (Falsy | ... 1 more ... | RegisteredStyle<...>)[]'.
      Type 'ViewStyle' is not assignable to type 'TextStyle'.
        Types of property 'userSelect' are incompatible.
          Type 'string | undefined' is not assignable to type '"text" | "auto" | "none" | "contain" | "all" | undefined'.
            Type 'string' is not assignable to type '"text" | "auto" | "none" | "contain" | "all" | undefined'.