Add interface information

[DL6ER]

What does this implement/fix?

This PR implements a Discourse feature request. The particular implementation is up for discussion and possible further improvements therewhile.

Needs pi-hole/FTL#2009 (branch tweak/api_network_info) to work.

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Related issue or feature (if applicable): https://discourse.pi-hole.net/t/list-ip-v4-and-v6-address-in-web-interface/70981/11

Pull request in docs with documentation (if applicable): N/A

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2. I have commented my proposed changes within the code.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
• I signed off all commits. Pi-hole enforces the DCO for all contributions
• I signed all my commits. Pi-hole requires signatures to verify authorship
• I have read the above and my PR is ready for review.

[DL6ER]

And an altogether new page which lists all interfaces, expanding interfaces by default which are connected to a default gateway (IPv4 and/or IPv6):

[yubiuser]

Both FF and chrome error on this PR, interestingly with different things to complain about.

[yubiuser]

The issue is fixed with the latest commits.
But the appearance is broken for midnight and high contrast dark theme. For deep-midnight the hover effect is to bright.

[rdwebdesign]

For deep-midnight the hover effect is to bright

At the moment, I'm not able to test the branch (this week is really busy) so I didn't see the issue, but looking at the code and the new CSS rules (style/vendor/bstreeview.min.css), I think the "too bright" issue is happening because the new elements use the same color for every theme:

.bstreeview .list-group-item:hover{background-color:#dee2e6}

Adding a new color to default-darker.css, with .bstreeview .list-group-item:hover {background-color: <new color>} should fix it.

When I have the time I will try to add a few CSS rules to fix this elements in the dark themes.