Add a link to the destination for symbolic links
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=18717)
</details>
<!--IssueSummary end-->
### Description
Currently (I'm talking about version 9.3) on GitLab a symbolic link in a repository will be basically
represented as a text file with the path it denotes.
This is helpful to understand the actual contents of the repository
but if one wants to view the contents of the file the link actually points to,
which is a quite common situation IMHO, he/she has to navigate there manually.
This is inconvenient if the repository is intended to be browsed in that way.
### Proposal
Since I don't think it's a correct behavior to follow the symbolic link transparently
and display the contents, I propose to either (better both)
(1) include a hyperlink on the content page of a symbolic link to the linked file,
or (2) while showing the path, display alongside the contents of the linked file
on the content page of a symbolic link.
### Links / references
### Documentation blurb
(although I have no idea what this section is supposed to be like,
let me attempt.)
Symbolic link support is enhanced by including a hyperlink to the actual file it
points to and showing a preview of the file contents instead of barely displaying
the path the symbolic link holds.
#### Use cases
For example I host a repository on my personal installation of GitLab
to store papers I've written. The PDFs of those papers are stored in folders
that also hold their corresponding source files. And I have a directory that list
finished papers with symbolic links to those PDFs. The hope is that if I view any of them
on the web interface of GitLab, I can preview the PDF easily, but instead, it will
display something like this currently:

which is definitely what I want for my purpose.
If any of the proposed feature is implemented, I will be happy
because I can then easily view the contents of the PDFs from
the index directory.
### Feature checklist
Make sure these are completed before closing the issue,
with a link to the relevant commit.
- [ ] [Feature assurance](https://about.gitlab.com/handbook/product/#feature-assurance)
- [ ] Documentation
- [ ] Added to [features.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml)
issue