refactor: Add correct typing

Author: xiCO2k

src/index.ts

@@ -1,4 +1,4 @@
-import { reactive } from 'vue'
+import { reactive, Plugin } from 'vue'
 import { OptionsInterface } from './interfaces/options'
 import { LanguageInterface } from './interfaces/language'
 import { ReplacementsInterface } from './interfaces/replacements'
@@ -89,8 +89,8 @@ export function trans(key: string, replacements: ReplacementsInterface): string
   return message
 }
 
-export const i18nVue: object = {
-  install: (app, currentOptions: OptionsInterface) => {
+export const i18nVue: Plugin = {
+  install: (app, currentOptions: OptionsInterface = {}) => {
     options = { ...options, ...currentOptions }
     app.config.globalProperties.$t = (key: string, replacements: ReplacementsInterface) => trans(key, replacements)
     loadLanguageAsync(options.lang)

src/interfaces/options.ts

@@ -4,6 +4,6 @@ import { LanguageJsonFileInterface } from './language-json-file'
  * The Interface that is responsible for the Options provided.
  */
 export interface OptionsInterface {
-  lang: string
-  resolve(lang: string): Promise<LanguageJsonFileInterface>
+  lang?: string
+  resolve?(lang: string): Promise<LanguageJsonFileInterface>
 }