Add documentation to vuejs roadmap (#6653)

* feat: add v-if documentation for Vue.js

* Update src/data/roadmaps/vue/content/v-if@xHj3W9Ig3MVuVlGyXchaP.md

* feat: add v-else documentation for Vue.js

* Update src/data/roadmaps/vue/content/v-else@0CtAZQcFJexMiJfZ-mofv.md

---------

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

src/data/roadmaps/vue/content/v-else@0CtAZQcFJexMiJfZ-mofv.md

@@ -1 +1,7 @@
-# v-else
+# v-else
+
+The `v-else` conditionally renders an element or a template fragment as a function in case the `v-if` does not fulfil the condition.
+
+Visit the following resources for more information:
+
+- [@official@v-else documentation](https://vuejs.org/api/built-in-directives.html#v-else)