feat: improve types (#47)

* feat: provide vuex types

`$moment` is injected using nuxt `inject` method and is therefore also available in `vuex`.

* feat: Improve types

This makes all the ways to use moment type-safe, e.g. this is now type-safe:
`this.$moment.duration(this.$moment(moment1).diff(moment2)).humanize()`

* chore(readme): Add instructions for typescript setup

* chore(readme): Add more details to typescript setup

* fix(types): Use vuex/types/index

* chore(readme): Typescript setup for nuxt > 2.9

README.md

@@ -52,6 +52,28 @@ export default {
 }
 ```
 
+### Typescript setup
+
+Add the types to your "types" array in tsconfig.json after the `@nuxt/types` entry.
+
+:warning: Use `@nuxt/vue-app` instead of `@nuxt/types` for nuxt < 2.9. 
+
+**tsconfig.json**
+
+```json
+{
+  "compilerOptions": {
+    "types": [
+      "@nuxt/types",
+      "@nuxtjs/moment"
+    ]
+  }
+}
+```
+> **Why?**
+>
+> For typescript to be aware of the additions to the `nuxt Context`, the `vue instance` and the `vuex store`, the types need to be merged via [declaration merging](https://www.typescriptlang.org/docs/handbook/declaration-merging.html) by adding `@nuxtjs/moment` to your types.
+
 ## Configuration
 
 To strip all locales except `en`:

types/index.d.ts

@@ -1,21 +1,28 @@
-import { Moment, MomentFormatSpecification, MomentInput } from 'moment'
+import moment from 'moment'
 import Vue from 'vue'
 
 declare module '@nuxt/vue-app' {
   interface Context {
-    $moment(input?: MomentInput, format?: MomentFormatSpecification, language?: string, strict?: boolean): Moment
+    $moment: typeof moment
   }
 }
 
 // Nuxt 2.9+
 declare module '@nuxt/types' {
   interface Context {
-    $moment(input?: MomentInput, format?: MomentFormatSpecification, language?: string, strict?: boolean): Moment
+    $moment: typeof moment
   }
 }
 
 declare module 'vue/types/vue' {
   interface Vue {
-    $moment(input?: MomentInput, format?: MomentFormatSpecification, language?: string, strict?: boolean): Moment
+    $moment: typeof moment
   }
 }
+
+declare module 'vuex/types/index' {
+  interface Store<S> {
+    $moment: typeof moment
+  }
+}
+