chore. Add target _blank to links

[pangolp]

Fixes #0000

Changes proposed in this pull request:

What I want to achieve with this pull request is that the links can have the corresponding HTML tag, so that they can be opened in another tab.

Reviewers should focus on:

This is my first time working with the community, so I may need some guidance, but if necessary, I'm willing to make any necessary changes to get the code working and merged.

Screenshot

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Related documentation PR: (Remove if irrelevant)

[pangolp]

Sorry, I'm closing this request because my intention was to contribute to the current branch, not the development branch. Perhaps this can be used in the future, when we migrate to version 2. If the code works, and they want to reopen the issue and merge it... I'm not opposed at all. But we're currently using the stable version and need to add this functionality to open links in different tabs.