Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51210

This suggests possibly related issues when the user types a title.

This uses GraphQL to allow the frontend to request the exact
data that is requires. We also get free caching through the Vue Apollo
plugin.

With this we can include the ability to import .graphql files in JS
and Vue files.
Also we now have the Vue test utils library to make testing
Vue components easier.

Closes #22071

This commit moves `mermaid` from blackst0ne-mermaid package to the
upstream version.

The reason why the fork was used was this bug[1].
The bug has been fixed, so there's no need to maintain my fork anymore.

[1]: https://github.com/knsv/mermaid/issues/584

https://github.com/vuejs/vue/releases

most relevant release notes are in the 2.5.17 beta post:
https://github.com/vuejs/vue/releases/tag/v2.5.17-beta.0