Embedded snippets: Allow use in GitLab comments
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### Description
We have a great new community contribution with our "Embedded snippets" feature, available with [10.8](https://about.gitlab.com/2018/05/22/gitlab-10-8-released/).
This feature has potential to be very useful within GitLab comments as well. Right now, `script` tags are suppressed for security reasons.
```html
<script src="https://gitlab.com/akaemmerle/example-project/snippets/1718255.js"></script>
```
### Proposal
Let's find a way to make this work within GitLab comments.
### Links / references
https://gitlab.com/gitlab-org/gitlab-ce/issues/8088
issue