Add a registration form.

src/components/registration/registration.js

@@ -0,0 +1,29 @@
+const registration = {
+  data: () => ({
+    user: {},
+    error: false,
+    registering: false
+  }),
+  methods: {
+    submit () {
+      this.registering = true
+      this.user.nickname = this.user.username
+      this.$store.state.api.backendInteractor.register(this.user).then(
+        (response) => {
+          if (response.ok) {
+            this.$store.dispatch('loginUser', this.user)
+            this.$router.push('/main/all')
+            this.registering = false
+          } else {
+            this.registering = false
+            response.json().then((data) => {
+              this.error = data.error
+            })
+          }
+        }
+      )
+    }
+  }
+}
+
+export default registration